AMC & GM to Part 21 — Issue 1, Amendment 9

ED Decision 2011/010/R 01/12/2011

European Aviation Safety Agency

DECISION NO 2011/010/R

amending Decision No. 2003/01/RM of the Executive Director of the Agency of

17 October 2003

on

Acceptable Means of Compliance and Guidance Material for the airworthiness and environmental certification of aircraft and related products, parts and appliances, as well as for the certification of design and production organisations (‘AMC and GM to Part-21’)

‘Improvement of GM to 21A.101’

(Establishment of the type-certification basis of Changed Aeronautical Products)

THE EXECUTIVE DIRECTOR OF THE EUROPEAN AVIATION SAFETY AGENCY,

Having regard to the Regulation (EC) No 216/2008 (hereafter referred to as the ‘Basic Regulation’), and in particular Article 38(3)(a) and (e) thereof, Having regard to the Commission Regulation (EC) No 1702/2003 , and in particular 21A.101 of the Annex (Part-21) thereof,

Whereas:

ED Decision 2011/010/R 01/12/2011

(1) The Agency shall, pursuant to Article 18 of the Basic Regulation, issue Certification Specifications and Acceptable Means of Compliance, as well as Guidance Material for the application of the Basic Regulation and its Implementing Rules. (2) The Agency is obliged, pursuant to Article 19 of the Basic Regulation, to reflect the state of the art and the best practices in the fields concerned and to update these documents taking into account the worldwide aircraft experience in service, and scientific and technical progress. (3) The rulemaking task 21.018 of the Agency resulted in a proposal to improve Guidance Material contained in GM 21A.101 ‘Establishment of the type-certification basis of Changed Aeronautical Products’ in order to better support application of the 21A.101 rule of Part-21. (4) The Agency, pursuant to Article 52(1)(c) of the Basic Regulation and articles 5(3) and 6 of the Rulemaking Procedure , has widely consulted interested parties on the matters that are subject of this Decision and has provided thereafter a written response to the comments received .

HAS DECIDED:

Article 1 The Annex ‘Acceptable Means of Compliance and Guidance Material to be used in the airworthiness certification of products, parts and appliances and the approval of organisations involved in their design or manufacture’ to Decision ED/2003/01/RM of the Executive Director of the Agency of 17 October 2003 is hereby amended as provided in Annex 1 to this Decision.

Article 2 th This Decision shall enter into force on 8 December 2011. It shall be published in the Official Publication of the Agency.

P. GOUDOU

ED Decision 2011/010/R

01/12/2011

EXECUTIVE SUMMARY

GM 21A.101, which is part of ‘AMC and GM to Part-21’, provides an extensive guidance material (GM) on establishment of the type-certification basis of Changed Aeronautical Products. This guidance supports application in certification projects of major changes to products of the 21A.101 rule of Part-21. The 21A.101, also referred to as ‘Changed Product Rule’ or ‘CPR’, deals with designation of applicable certification specifications and environmental protection requirements for the type-certification basis. Both the CPR rule 21A.101 and the guidance GM 21A.101 are to a large extent harmonised with the corresponding rules and guidance of the Federal Aviation Administration (FAA) and Transport Canada (TCCA). They have not been amended since their adoption in 2003. Experience gained by all three Authorities since 2003 from application of the above rule and guidance in CPR certification projects of changed products indicated there was a need for improvements of the guidance material to address certain implementation problems identified. The Agency, the FAA and TCCA agreed to set up a joint team in 2007 under the name ‘CPR International Implementation Team’ (CPR-IIT). The CPR-IIT was tasked to reflect on the experience gained by the three authorities from overseeing CPR implementation and consider harmonised changes to the existing guidance material and internal policies. The Agency included into its Rulemaking Programme the rulemaking task 21.018 ‘Improvement of GM to 21A.101’ with the aim to develop and include into GM 21A.101 the improved and harmonised text developed by the CPR-IIT. The proposal was published as NPA 2010-02 in March 2010 and followed the standard consultation process resulting in publication of the respective CRD in January 2011. The feedback from the NPA consultation did not indicate a major opposition to the amended GM text as a whole but some comments proposed text changes. Quite a number of useful comments were accepted by the Agency which lead to improvement of the the text. The Agency received two reactions on the CRD. One reaction requested withdrawal of the proposal, preparation with STC industry of a new text and another round of NPA/CRD consultation. The Agency’s responses to these reactions are contained in the explanatory note.

The new text of GM 21A.101 introduced by this Decision brings an improved guidance for application of the 21A.101 rule.

ED Decision 2011/010/R 01/12/2011

Annex 1 to ED Decision 2011/010/R

The Annex ‘Acceptable Means of Compliance and Guidance Material to be used in the airworthiness certification of products, parts and appliances and the approval of organisations involved in their design or manufacture’ to Decision ED/2003/01/RM of the Executive Director of the Agency of 17 October 2003 is hereby amended as follows:

The text of amendments is arranged to show deleted text or new text as shown below:

1. Text to be deleted is shown with a strikethrough.

2. New text to be inserted is highlighted with grey shading.

3. … Indicates that remaining text is unchanged in front of or following the reflected amendment.

The existing main body of GM 21A.101 is replaced with the following:

GM 21A.101 Establishing the type-certification basis of Changed Aeronautical Products

Foreword

This guidance material (GM) provides guidance for the application of the Changed Product Rule, 21A.101 and 21A.19, for changes made to type-certificated aeronautical products.

Chapter 1. Introduction

1. Purpose

a. The Agency wrote this GM to provide guidance for establishing the type-certification basis

for changed aeronautical products in accordance with 21A.101 and to help identify if it will be necessary to apply for a new type-certificate (TC) under 21A.19. The guidance describes the process for establishing the type-certification basis for changes to type certificates or restricted type-certificates, supplemental type certificates (STC) and amended STCs, detailing

evaluations, classifications, and decisions made throughout the process.

b. The content of this GM is divided into 4 Chapters and 5 Appendices:

(1) Chapter 1 explains the purpose of this GM, describes its content, specifies the intended audience, and clarifies which changes are within the scope of applicability of this GM. Chapter 1 also contains definitions and terminology used in this GM for application of 21A.101 and 21A.19. (2) Chapter 2 provides a general overview of 21A.101 and 21A.19, clarifies the principles and safety objectives and directs applicants to the applicable guidance contained in subsequent chapters of this GM. (3) Chapter 3 contains guidance for implementation of 21A.101(b) to establish the type-certification basis for changed aeronautical products. Chapter 3 describes in detail the various steps of the “top-down” certification basis development approach. Chapter 3 also addresses 21A.19 considerations to identify conditions under which an applicant for a type

ED Decision 2011/010/R

01/12/2011

design change is required to submit application for a new TC and provides guidance at which stage of the process this assessment is to be performed.

(4) Chapter 4 contains considerations for design related operating requirements, guidance for establishing type-certification basis for changes on certain small aeroplanes and rotorcraft under specified maximum weight (“excepted products”), guidance for use of special conditions under 21A.101 (d), guidance on the effective period of an application, guidance for establishing the type-certification basis for changes on aircraft designed or modified for a special purpose (to operate under a restricted certificate of airworthiness) and guidance for documentation of revisions to the type-certification basis. (5) Appendix A contains examples of typical type design changes for small aeroplanes, large aeroplanes, rotorcraft, engines, and propellers which are categorised by the Agency into individual tables according to the classifications to the level of design change - substantial, significant, and not significant. (6) Appendix B provides detailed guidance with examples for evaluating when compliance would be impractical under the “impracticality” exception in the rule.

(7) Appendix C provides guidance with examples on use of relevant service experience in the certification process as one way to show that a later amendment may not contribute materially to the level of safety, allowing the use of earlier certification specifications. (8) Appendix D contains figures and tables considered useful for understanding of the basic terms used and their mutual relations to assist correct application of this GM. (9) Appendix E contains cross references to relevant requirements of Part-21 related to application of 21A.19 and 21A.101.

c. This GM describes an acceptable means, but not the only means to comply with 21A.101

and 21A19. However, if an applicant chooses to use the means described in this GM, they must

follow it entirely.

2. Audience

This GM is for applicants applying for:

- major changes to type design of products under 21A.97 and to type design of Auxiliary Power Units (APUs) under 21A.604(b)), - supplemental type-certificates (STCs) under 21A.113, or - major changes to STCs under 21.117 (b).

3. Applicability

a. Reserved.

b. This GM applies to major type design changes under 21A.101 for aeronautical products

type-certificated, restricted type-certificated, supplemental type-certificated or ETSO approved (APU) under Part-21 (ref. 21A.21. 21A.23, 21A.115, 21A.604), with application for the typecertification basis of the airworthiness code of the applicable CS (CS-VLA, CS-22, CS-23, CS- 25 etc.).

c. Minor type design changes are automatically considered not significant under 21A.101(b)

and the existing type-certification basis is considered adequate for their approval under 21A.95.

d. Reserved.

ED Decision 2011/010/R 01/12/2011

e. For the purpose of this GM, the term aeronautical products, or products, means type-

certificated or restricted type-certificated aircraft, engines, and propellers or ETSO approved APUs.

f. This GM is not intended to be used to determine the applicable environmental protection

requirements (aircraft noise, fuel venting and exhaust emission requirements) for changed products.

4. Definitions and Terminology.

Adequate Type-certification Basis – The type-certification basis for a changed product

under 21A.101 is considered adequate when the Agency determines that it provides adequate standards for the design change, i.e. when the certification specifications of the applicable airworthiness code and prescribed special conditions provide an appropriate level of safety for the changed product and do not result in any unsafe design features.

Aeronautical product – The terms aeronautical product or product(s) used in this guidance

material include type-certificated or restricted type-certificated aircraft, engines, propellers and ETSO approved Auxiliary Power Units (APUs).

Affected area, system, part or appliance – any system, part, or appliance which is either

physically altered by a proposed design change or, even if not altered physically, its functional characteristics are altered due to the effects of the physical change.

Design change – A change in the type design of an aeronautical product. In the context of

this document the terms “change”, “design change” and “type design change” are synonymous.

Earlier certification specifications – The certification specifications of the applicable

airworthiness code in effect prior to the date of application for the change, but not prior to the existing type-certification basis.

Existing type-certification basis – The certification specifications of the applicable

airworthiness code, special conditions and equivalent level of safety findings incorporated by reference in the type-certificate of the product to be changed.

Latest certification specifications – The certification specifications of the applicable

airworthiness code in effect on the date of application for the change.

Previous relevant design changes – Previous design changes, the cumulative effect of

which could result in a product significantly or substantially different from the original product or model, when considered from the last time the latest certification specifications were applied.

Product level change – A change or combination of changes that makes the product distinct

from other models of the product (for example, range, payload, speed, design philosophy). Product level change is defined at the aircraft, engine, propeller, or APU level of change.

Secondary change – A change is a secondary change if compliance to the latest amendment

would not contribute materially to the level of safety UUUUand where it is part of and consequential to an overall significant change. A secondary change is a physical change that restores without changing the system, structural capacity, or functionality, but is necessary to support a significant change.

ED Decision 2011/010/R

01/12/2011

Significant change – A change to the type-certificate significant to the extent that it changes

at the product level one or more of the following: general configuration, principles of construction, or the assumptions used for certification, but not to the extent to be considered a substantial change. The significance of the change must be considered in the context of all previous relevant design changes and all related revisions to the certification specifications of the applicable airworthiness code. Not all product level changes are significant.

Significant change in an area (for excepted aircraft under 21A.101(c) only) – A change in

an area is significant if the general configuration or the principles of construction in that area are not retained, or the assumptions used for certification of that area do not remain valid.

Substantial change – A change which is so extensive that a substantially complete

investigation of compliance with the applicable type-certification basis is required, and consequently a new type certificate, in accordance with 21A.19.

Type-certification basis – The certification specifications of the applicable airworthiness code

as established in 21A.17 and 21A.101, as appropriate; special conditions; and equivalent level of safety findings applicable to the product to be certificated.

Chapter 2. Overview of 21A.19 and 21A.101

1. 21A.19

a. 21A.19 requires an applicant to obtain a new type-certificate (TC) for a changed product if

the change in design, power, thrust, or weight is found by the Agency so extensive that a substantially complete investigation of compliance with the applicable type-certification basis is required.

b. Changes that require a substantial re-evaluation of the product’s compliance findings are

referred to as “substantial changes”. For guidance, see section 3 of Chapter 3. Appendix A to this GM provides examples of type design changes that will require application for a new TC.

c. If the Agency has determined through 21A.19 that the proposed design change does not

require a new TC, see 21A.101 for the applicable implementing rules to establish the typecertification basis for the proposed design change. For guidance, see Chapter 3 and the examples in Appendix A of this GM.

2. 21A.101

a. 21A.101(a) requires a change to a TC to comply with the latest certification specifications,

unless the change meets the criteria for the exceptions identified in 21A.101(b) and (c). The intent of 21A.101 is to enhance safety through the incorporation of the latest regulatory standards in the type-certification basis for changed products to the greatest extent practicable.

b. An applicant can comply with certification specifications of an earlier amendment of the

airworthiness code consistent with the requirements of 21A.101(b), when: • a change is not significant (see 21A.101(b)(1)), or

• an area, system, part or appliance is not affected by the change (see 21A.101 (b) (2)), or • compliance with the latest amendment for a significant change does not contribute materially to the level of safety (see 21A.101(b)(3)), or

• compliance with the latest amendment would be impractical (see 21A.101(b)(3)).

ED Decision 2011/010/R

01/12/2011

c. Note that earlier amendments may not precede the corresponding amendment of the

airworthiness code incorporated by reference in the type-certificate.

d. 21A.101(b) allows a changed product to comply with an earlier amendment of the

applicable airworthiness code, provided one of the criteria in 21A.101(b)(1),(2) or (3) are met and the earlier amendment is considered adequate. However, when a proposed design change involves features or characteristics considered novel or unusual, or the intended use of the changed product is unconventional, or experience from other similar products in service or products having similar design features has shown that unsafe conditions may develop, and the proposed airworthiness standards do not contain adequate or appropriate standards for the changed product, later amendments and/or special conditions will be applied.

e. 21A.101(b)(1)(i) and (ii) describe the automatic criteria establishing that a change is

significant.

f. 21A.101(c) provides an exception from the requirements of 21A.101(a) for a change to

certain aircraft with less than specified maximum weight. If an applicant applies for a type design change to an aircraft (other than rotorcraft) of 2 722 kg (6 000 pounds) or less maximum weight, or to a non-turbine powered rotorcraft of 1 361 kg (3 000 pounds) or less maximum weight, the applicant can show that the changed product complies with the typecertification basis incorporated by reference in the TC. The applicant can also elect to comply, or may be required to comply, with a later amendment. See chapter 4, section 2 in this GM for specific guidance on this provision.

g. 21A.101(d) provides for the use of special conditions, under 21A.16B, when the proposed

amendment of the applicable airworthiness code and any later amendment do not provide adequate standards to the proposed change.

h. 21A.101(e) prescribes the effective period an application will remain valid for a change. This section is consistent with the requirements of 21.17 for a new TC.

Chapter 3. The Process for Establishing the Type-certification Basis for Changed Products 21A.101 (a) and (b)

1. Overview

a. Both the applicant and the Agency have responsibility under 21A.101(a) and (b). The

applicant must show that the change complies with the latest applicable certification specifications unless use of an exception per 21A.101(b) is justified. If an exception is proposed, the applicant should make a preliminary classification whether the change is significant or not significant, and propose an appropriate type-certification basis. The Agency determines whether the applicant’s classification of the change and proposal for the typecertification basis are consistent with the applicable rules and their interpretation, but should not be dependent on whether the TC holder or applicant for a STC is originating the change. The type-certification basis can vary depending on the magnitude and scope of the change. The steps below present a streamlined approach for making this determination. In addition to assisting in the determination of significance and establishing the type-certification basis, this guidance will help to establish the appropriate amount of coordination required between the applicant and the Agency.

b. Classifications of typical type design changes are in Appendix A, Classification of Changes.

See paragraph 6(c) of this chapter for instructions on how to use Appendix A.

ED Decision 2011/010/R 01/12/2011

c. In cases where the examples in Appendix A are not applicable for the proposed change, use

the following steps in conjunction with Figure 1 on the next page to establish the appropriate

type-certification basis for the type design change.

ED Decision 2011/010/R

01/12/2011

Figure 1. Establishing the Type-certification Basis for Changed Product

ED Decision 2011/010/R

01/12/2011

2. Step 1 of Figure 1. Identify The Proposed Type Design Change To An Aeronautical Product

a. Prior to describing the proposed change(s), it is important to clearly identify the type design

configuration to be changed. A series of derivative aircraft, engines, or propellers (for example, x-100, x-200, x-300) may evolve based on predecessor type designs, each with its own design changes that make it distinct from the other series. The applicant should identify which model or series within that model is the specific configuration that will be modified.

Note: An STC is not a product; it is a change to a product.

When changing or amending an STC the starting point is the existing modified product (TC with existing STC installed). For example, if an applicant were amending an STC for an external cargo locker and the applicant proposed changing the configuration of the locker, then the starting point would be the existing TC with the existing STC installed. The applicant would then compare that configuration (TC with existing STC installed) to the changed product (TC with proposed amended STC installed).

b. Changes to a product can include physical design changes, changes to an operating

envelope and/or performance changes. The change can be a single change or a collection of changes. The purpose of this process step is to identify and describe the change to the aeronautical product. The applicant for a type design change should consider all previous related design changes and the amendment level of the type-certification basis for these changes.

ED Decision 2011/010/R

01/12/2011

Note 1: By definition all previously incorporated changes have been approved. The purpose of

step 1 is to consider the net cumulative effect of the changes since the last time the certification basis for the changed/affected area was upgraded from that of the original type design.

Note 2: Substantiating data for the proposed type design change can include compliance

findings from a previously approved design change, in supporting compliance findings for the proposed change. However, for the purpose of classifying the proposed design change, such previously approved design and compliance data should be now considered in relation to the proposed type design change and should be taken into account as a part of the proposed design change classification.

c. When identifying the changes being proposed as part of a modification, consider previous

relevant changes that create a cumulative effect, as these may influence the decisions regarding substantial and significant changes later in the process. By previous relevant changes those design changes are meant whose effects accumulate, such as successive thrust increases, incremental weight increases, or sectional increases in fuselage length. Any previous relevant design changes in the area affected by the current change that did not involve an upgrade of the existing type-certification basis should be taken into account in the next design change proposal.

(1) Example 1: A 5 % weight increase is currently being proposed, but a previous 10 % and

another 15 % weight increase has been incorporated into this aircraft without upgrading the existing type-certification basis. In the current proposal for a 5 % weight increase, the cumulative effects of the two previous weight increases that did not involve upgrade of the type-certification basis will now be accounted for as an approximately 30 % increase in weight, for the purpose of making the substantial and/or significant decisions. Note that the cumulative effects to be considered are only those incremental increases from the last time the applicable certification specifications in the type-certification basis were upgraded.

(2) Example 2: The TC for aeroplane model X lists three series, namely X-300, X-200, and X-

100. The X-300 is a derivative of the X-200 which is a derivative of the original X-100 series. An applicant proposes a design change to the X-300 series aeroplane. During the review of the X-300 type-certification basis and the certification specifications affected by the proposed change, it was identified that one certification specification, CS-25.571 (damage tolerance), remained at the same amendment level as the X-100 original type-certification basis (derogation from 21A101(a) was allowed). Since the amendment level for this particular certification specification was not changed for the two subsequent aeroplane series (X-200 and X-300), the cumulative effects of these two previous design changes that are related to the proposed change and the damage tolerance requirements should now be addressed.

d. To identify and describe the proposed changes to any aeronautical product, use a high-level

description of the design change that characterises the intent of, or the reason for, the change. No complex technical details are necessary at this stage. For example, a proposal to increase maximum passenger-carrying capacity may require an addition of a fuselage plug, and as such a “fuselage plug” becomes one possible high-level description of this design change. Similarly, a thrust increase, a complete new interior, an avionics system upgrade, or a passenger-tocargo conversion are all high-level descriptions that characterise typical changes to the aircraft, each driven by a specific goal, objective or purpose.

e. Evolutionary Changes. Evolutionary changes that occur during the course of a certification

programme may require re-evaluation of the type-certification basis and may result in reclassification of the change. That is, any evolution in the proposed design change after the type-certification basis has been agreed to (or established) will necessitate a revisit of the type-certification basis to ensure that “evolved” aspects of the design change are still covered by the agreed upon certification basis.

ED Decision 2011/010/R

01/12/2011

3. Step 2 of Figure 1. Is the change substantial?

a. 21A.19 requires an applicant to apply for a new TC for a changed product if the proposed

change in design, power, thrust, or weight is so extensive that a substantially complete investigation of compliance with the applicable regulations is required. A new TC could be required for either an extensive change to a previously type-certificated product or for a changed design derived through the cumulative effect of a series of design changes from a previously type-certificated product.

b. A ‘substantially complete investigation’ of compliance is required when most of the existing

substantiation is not applicable to the changed product. A substantial change proposal will require the need to comply with all the certification specifications applicable to a particular category of product. The number of certification specifications to which compliance must be reestablished for the changed product may not necessarily be the sole determination criteria as to whether the change is substantial, but rather the extent of effort to establish compliance, or the depth of investigation required to be done. In other words, the design change may be considered substantial if it is so extensive (making the product sufficiently different from its predecessor) that the design models, methodologies and approaches used to demonstrate a previous compliance finding could not be used.

c. To address the question if a change is substantial at the beginning of the process, the

applicant should evaluate the total or combined effect of all the proposed changes identified in Step 1, including the cumulative effects of previous relevant design changes since the last update of the type-certification basis (as explained in Step 1).

d. If it is not initially clear that a new TC is required, Appendix A provides some examples of

substantial changes to aid in this classification. A substantial change requires application for a new TC under 21A.17 and 21A.19. If the change is not substantial, then follow the 21A.101 process.

4. Step 3 of Figure 1. Will the Latest Certification Specifications be Used?

a. The applicant can use the latest certification specifications for their proposed type design

change. If the latest certification specifications are used, the applicant will meet the intent of 21A.101 and no further classification (significant or not significant) and justification is needed. However, the decision to voluntarily comply with the latest certification standards for a design change sets a new regulatory baseline for all future related changes in the same affected area. Even though one applicant elects to use the latest certification requirements, another applicant could apply 21A.101 for a similar design change proposal, and use the exceptions in accordance with 21A.101(b). If the latest certification specifications are not used, then proceed as follows:

ED Decision 2011/010/R

01/12/2011

5. Step 4 of Figure 1. Relation of Changes

a. Once the proposed changes are identified using high-level descriptions, the next step is to

determine if any of these changes are related to each other. Related changes are those that cannot exist without one another, are co-dependent, or a prerequisite of one another. For example, a need to carry more passengers could require the addition of a fuselage plug, which will result in a weight increase, and may necessitate a thrust increase. Thus the fuselage plug, weight increase and thrust increase are all related high-level changes that will be needed to achieve the goal of carrying more passengers. A decision to upgrade the cockpit to more modern avionics at the same time as these other design changes may be considered unrelated, as the avionics upgrade is not necessarily needed to carry more passengers (it has a separate purpose, likely just modernisation). The proposed avionics upgrade would then be considered an unrelated (or a stand-alone) change. However, the simultaneous introduction of a complete new interior may be considered related since a cabin length change will have an impact on occupant safety considerations. Even if a new cabin interior is not included in the product level change, the functional effect of the fuselage plug has implications on occupant safety (e.g., the dynamic environment in an emergency landing, emergency evacuation, etc.), and thus the cabin interior becomes an affected area.

b. Once the change(s) are organised into groupings of those that are related and those that

are unrelated (or stand-alone), the applicant is ready for Step 5 of Figure 1. The grouping of related and unrelated changes is particularly relevant to the significant Yes/No decision, (21A.101(b)(1)), described in Step 5 of Figure 1. Each group of related changes and each unrelated (stand-alone) change is evaluated on its own merit for significance.

c. After describing the groupings and the associated or supporting technical details for each

change, the applicant should identify areas, systems, parts or appliances of the product that are affected by the design change and the corresponding certification specifications associated with these areas. For each group, the applicant should assess the physical and/or functional effects of the change on other areas, systems, parts, or appliances of the product. The characteristics affected by the change are not only physical changes, but also functional changes brought about by the physical changes. Examples of physical aspects are: structures, systems, parts and appliances, software in combination with the affected hardware. Examples of functional characteristics are performance, handling qualities, aeroelastic characteristics, and emergency egress. The intent is to encompass all aspects where there is a need for reevaluation, that is, where the substantiation presented for the product being changed should be updated or rewritten.

6. Step 5 of Figure 1. Is the Proposed Change Significant? (21A.101(b)(1))

a. In Step 5 it is the applicant’s responsibility to justify that a grouping of related changes or

an unrelated change does not qualify as a significant change. Significant changes are product level changes which are distinct from the vast majority of major changes. In general, these

ED Decision 2011/010/R

01/12/2011

changes are either the result of an accumulation of changes or occur through an isolated extensive change that makes the changed product distinct from its predecessors. Step 1 explains the accumulation of changes that should be considered. 21A.101(b)(1) defines a significant change as existing when one or more of three automatic criteria apply:

(1) Changes where the general configuration is not retained (significant change to general configuration). A change to the general configuration at the product level that

distinguishes the resulting product from other product models, for example performance or interchangeability of major components. Typically, for these changes an applicant will designate a new aircraft model number, although this is not required. For examples, see Appendix A to this GM.

(2) Changes where the principles of construction are not retained (significant change to principles of construction). A change at the product level to the materials

and/or construction methods that affect the overall products’ operating characteristics or inherent strength and would require extensive reinvestigation to show compliance. For examples, see Appendix A to this GM.

(3) Changes that invalidate the assumptions used for certification (significant change to the assumptions used for certification). A change to the assumptions at

the product level associated with the compliance demonstration, performance or operating envelope that by itself is so different that the original assumptions or methodologies of

demonstrating compliance are invalidated. For examples, see Appendix A to this GM.

Note: The word “assumptions” in 21A.101 bears a meaning different from CS E-30 and CS-

P-30. CS-E and CS-P address the conditions that may be imposed on the engine or propeller when it is eventually installed in the aircraft and are published in the installation manual.

b. The above criteria are used to determine if each change grouping and each stand-alone

change is significant. These three criteria are assessed at the product level. In applying the automatic criteria the applicant should focus on the design change itself. Consideration of only the regulatory importance or safety benefit of the latest certification specifications is not a justification by itself to cause a design change to be classified or re-classified as a significant change.

c. Appendix A includes tables of typical changes for large aeroplanes, small aeroplanes,

rotorcraft, and engines/propellers that meet the definition of significant. The appendix also includes typical changes that do not achieve the significant level. In these tables, one or more of the three automatic criteria in 21A.101(b)(1) apply for each case where the changes are identified as significant. Experience has shown the concept of having only the three automatic criteria seems to fit most projects. The tables can be used in one of two ways:

(1) To classify a proposed change that is listed in the table, or

(2) In conjunction with the three automatic criteria, to help classify a proposed change not listed in the tables of the appendix by comparing the proposed change to changes which are similar in type and/or magnitude.

d. Design changes can trigger one or more of the automatic criteria listed in 21A.101(b)(1)(i)

and (ii) for the proposed design change. When assessing the design change grouping, consider the cumulative effect of previous relevant design changes. Design changes may have been incorporated over time with no change in the type-certification basis and the final product may be significantly different than would be represented by the existing type-certification basis.

e. Each grouping of related changes and each unrelated (stand-alone) change, identified using

high-level descriptions, will be evaluated to determine if it is a significant or not significant

ED Decision 2011/010/R

01/12/2011

change. Use the tables in Appendix A as guidance to make the classification of significant or not significant. Only when one or more of the three criteria is met, the type design change can be considered significant for that grouping or unrelated change. The starting point for assessing the cumulative effects of previous relevant design changes is from the last time the applicable certification specifications in the type-certification basis for the affected area, system, part, or appliance were upgraded.

f. Typically, a change to a single area, system, part or appliance may not result in a product

level change. However, there may be distinct cases where the change to a single system or part may, in fact, result in a significant change due to its effect on the product overall. Examples may include addition of winglets, leading edge slats or change in primary flight controls to fly-by-wire system.

g. A change is a secondary change if compliance to the latest amendment does not contribute

materially to the level of safety and where it is part of and consequential to an overall significant change. A secondary change is a physical change that restores without changing the system, structural capacity or functionality, but is necessary to support a significant change. Based on this description, a secondary change is not required to comply with the latest certification specifications because it is considered “not contributing materially to the level of safety”, and therefore eligible for an exception under 21A.101(b)(1)(3). Determining whether a change meets the description for secondary change, and thus is eligible for an exception, should be straightforward. Hence the substantiation or justification need only be minimal. If this determination is not straightforward, then the proposed change is very likely not a secondary change.

(1) In some cases the change which restores functionality may in fact contribute materially to the level of safety by meeting a later amendment. If this is the case, it would not be considered a secondary change.

(2) An example of secondary change is lengthening existing control cables passing through the new fuselage plug to restore existing functions to systems that could be situated within or beyond the new plug. The lengthening of these cables can be accepted as not adding system capacity or capability, so these changes can be identified as secondary changes and not be required to meet the latest amendment.

h. A new model number designation to a changed product is not necessarily indicative that the

design change is significant under 21A.101. Conversely, retaining the existing model designation does not mean that the design change is not significant. All changes are considered in light of the magnitude of the type design change.

i. Making the determination. The final determination of whether a design change is significant

or not significant is retained by the Agency. To assist the applicant in their assessment, the Agency has predetermined the classification of several typical design changes that can be used for reference, and these examples are listed in Appendix A to this GM.

j. At this point, the determination of significant or not significant for each of the groupings of

related changes and each stand-alone change has been made. For significant changes, if the applicant proposes to comply with an earlier requirement, the procedure outlined in paragraph 7 below should be used.

7. Proposing an Amendment Level for a Significant Change

a. If an unrelated (stand-alone) change or a grouping of related changes is classified as

significant, the applicant will comply with certification specifications of the latest amendment of the applicable airworthiness code for certification of the changed product, unless the applicant can justify use of one of the exceptions provided in 21A.101(b)(2) and/or (3) to show compliance with earlier amendment(s). The final type-certification basis may consist of a

ED Decision 2011/010/R

01/12/2011

combination of certification specifications of the applicable airworthiness code at different amendment levels ranging from the original type-certification basis to the most current amendments.

b. If the classification of the change is significant, all areas, systems, parts or appliances

affected by the change must comply with certification specifications of the applicable airworthiness code at the amendment level in effect on the date of application for the change. The applicant will need to show that an area, system, part or appliance is not affected by the change to justify use of the exception in 21A.101(b)(2) (see Section 9 for guidance on whether or not an area is affected by the proposed change).

c. Reserved.

d. 21A.101(b)(3) provides two more exceptions applicable to areas, systems, parts or

appliances which are affected by the significant change but for which compliance with the latest requirements would either not contribute materially to the level of safety or would be impractical (see Section 10 for more guidance).

e. Reserved.

f. The applicant should provide acceptable justification for the application of earlier

amendments for areas affected by a significant change. Your justification should show that compliance with later amendment in these areas would not contribute materially to the level of safety or would be impractical. Such justification should address all the aspects of the area, system, part or appliance affected by the significant change.

g. The final type-certification basis may combine certification specifications at the latest

amendment level, earlier (intermediate) amendment levels, and the amendment level of the existing type-certification basis, but cannot contain certification specifications preceding the existing type-certification basis.

h. Note that should an applicant decide to use the latest certification specifications without any

exceptions, no further evaluations and justifications are needed. In such a case, proceed to step 8 (section 11).

8. Proposing an Amendment Level for a Not Significant Change

a. When a change is classified not significant, the rule (21A.101(b)(1)) allows the use of the

earlier certification specifications, but not dated prior to the existing type-certification basis. Within this limit, the applicant is allowed to propose an amendment level for each certification specification for the affected area. However, the applicant should be aware that their proposal for the type-certification basis will be reviewed by the Agency to ensure that the typecertification basis is adequate for the proposed change (see paragraph 8.d).

b. Reserved

c. When choosing the above option of the existing type-certification basis, an applicant can

elect to comply with a specific certification specification or a subset of certification specifications at later amendments. In such a case, the applicant should consult with the Agency to ensure the type-certification basis includes other certification specifications that are directly related. Some later certification specifications may be less restrictive; therefore, the applicant may see advantage in using them on the elect to comply basis. However, the applicant is recommended not to make a final decision until they have learned from the Agency which other certification specifications are considered directly related.

d. For a design change that contains features which are not covered in the proposed type-

certification basis, i.e. when the type-certification basis is not considered “adequate” (see the

ED Decision 2011/010/R

01/12/2011

definition of “adequate type-certification basis” in 1.d of Chapter 1), the Agency will designate the applicable certification specifications at the appropriate amendment level, beginning with the existing type certification basis and progressing to the most appropriate later amendment level for the change. For a change that contains new design features that are novel or unusual, for which there is no later applicable certification specification, the Agency will designate special conditions.

9. Step 6 of Figure 1. Is the Area Affected By the Proposed Change? (21A.101(b)(2))

a. A not affected area is any area, system, part, or appliance that is not affected by the

proposed type design change. For a type design change, it is important that the effects of such change on other areas, systems, parts, or appliances of the product are properly assessed because areas that have not been physically changed may still be considered part of the affected area. If a new compliance finding is required, regardless of its amendment level, it is an affected area. If the significant change does not affect the area, then the type-certification basis of that area does not need to be revisited, in other words, the unaffected area continues to comply with the existing amendment level without further substantiation.

b. To determine whether an area is affected or not, consider the following aspects of a type

design change:

(1) Physical aspects. The physical aspects include direct changes to structures, systems, parts, and appliances (physical aspects may include software/airborne electronic hardware changes and the resulting effect on systems functions).

(2) Performance/functional characteristics. The less obvious aspect of the word “areas” covers general characteristics of the type-certificated product, such as performance features, handling qualities, emergency egress, structural integrity, aeroelastic characteristics, or crashworthiness. These characteristics may be affected by a product level change. For example, adding a fuselage plug could affect performance and handling qualities, and thus specifications associated with these aspects would be considered part of the affected area. Another example is the addition of a fuel tank and new fuel conditioning unit. This change affects the fuel transfer and fuel quantity indication system resulting in the aeroplane’s unchanged fuel tanks being affected. Thus, the entire fuel system (changed and unchanged areas) becomes part of the affected area due to the change in functional characteristics.

Note: Substantiating data for the affected area for a proposed type design change can

include compliance findings from a previously approved design change, in supporting compliance findings for your proposal. However, your proposal to use previously approved compliance data must be considered part of the entire proposed type design change and should be approved as part of your proposed design change.

c. All areas affected by the proposed design change must comply with the latest certification

specifications, unless the applicant can show that demonstrating compliance with the latest amendment of a certification specification would not contribute to the level of safety or would be impractical. Step 7 provides further explanation.

ED Decision 2011/010/R

01/12/2011

10. Step 7 of Figure 1. Are the Latest Certification Specifications Practical and Do They Contribute Materially to the Level of Safety? (21A.101(b)(3))

a. Compliance with the latest certification specifications could be considered ;not to contribute

materially to the level of safety if the existing type design and/or relevant experience demonstrates a level of safety comparable to that provided by the latest certification specifications. The applicant should provide sufficient justification to allow the Agency to make this determination. This exception could be applicable in the situations described in the

paragraphs below:

Note: Compliance with later certification specifications would not be required where the

amendment is of administrative nature and has been made only to correct inconsequential errors or omissions, consolidate text, or clarify an existing certification specification.

(1) Design features that exceed the existing type-certification basis specifications, but do not meet the latest certification specifications, can be used as a basis for granting an exception under the “does not contribute materially” exception. These design features, if accepted as a justification for an exception, must be incorporated in the amended type design configuration and recorded in the TCDS or STC, where necessary, as an integral part of the type-certification basis. For example , an applicant proposes to install winglets on a Part-25 airplane. Part of the design involves adding a small number of new wing fuel tank fasteners. The latest § 25.981 at amendment 25-102 requires structural lightning protection. The applicant proposes an exception from these latest structural lightning protection requirements because the design change uses new wing fuel tank fasteners with cap seals installed. The cap seal is a design feature that exceeds the requirement of § 25.981 at a previous amendment level, but does not meet the latest amendment 25- 102. If the applicant can successfully substantiate that compliance with amendment 25- 102 would not materially increase the level of safety of the changed product, then this design feature can be accepted as an exception to compliance with the latest amendment.

(2) Consistency of design should be considered when applying the latest certification specifications. Below, an aeroplane example is provided for describing how this provision may be used; however, the rationale in this example may be applied to any product covered by this GM.

 For example, when a small fuselage plug is added, additional seats and overhead bins are likely to be installed, and the lower cargo hold extended. These components may be identical to the existing components. The level of safety may

This example is taken from the FAA experience gained prior to the Agency’s start, therefore the references to the FAA sections and amendments are kept.

ED Decision 2011/010/R

01/12/2011

not materially increase by applying the latest certification specifications.

• However, if a fuselage plug is large enough in relation to the original certificated aircraft structure, seats, bins, doors, and cargo compartment, the change may require compliance with the latest certification specifications, comparable with what will be required for a new aeroplane. In these circumstances the proposed type-certification basis should encompass the certification specifications in effect on the date of application for the change.

(3) Service experience: Relevant service experience, such as fleet performance or utilisation over time (relevant flight hours or cycles), is one way of showing that a later amendment may not contribute materially to the level of safety, so the use of earlier certification specifications could be appropriate. Appendix C provides additional guidance on the use of service experience, along with examples.

• There may be cases for rotorcraft and small aeroplanes where relevant data may not be sufficient or not available at all because of the reduced utilisation and the different amount and type of data available. In such cases, other service history information may provide sufficient data to justify the use of earlier certification specifications, such as: warranty, repair, and parts usage data; accident, incident, and service difficulty reports; service bulletins; airworthiness directives; or other pertinent and sufficient data collected by the manufacturers, authorities, or other entities.

• The service experience levels necessary to demonstrate the appropriate level of safety as they relate to the proposed design change would have to be reviewed and agreed to by the Agency.

b. Impractical. Compliance with the latest certification specifications may be considered

impractical if the applicant can justify that it would result in additional resource requirements that are not commensurate with the incremental safety benefit (difference between the latest and the proposed type-certification basis). The additional resource requirements could include those arising from design changes required for compliance and the effort required to demonstrate compliance, but excludes resource expenditures for prior product changes.

(1) The position that compliance is impractical should be supported with a substantiating data and analyses. While evaluating the applicant’s position and their substantiating data regarding impracticality, the Agency may consider other factors (for example, the costs and safety benefits for a comparable new design).

(2) A review of large aeroplane projects showed that in certain cases, where an earlier amendment to applicable certification specifications was allowed, design changes were made to nearly comply with the latest amendments. In these cases, the applicants were able to successfully demonstrate that full compliance would require a substantial increase in the outlay or expenditure of resources with a very small increase in the level of safety. These design features can be used as a basis for granting an exception under the “impracticality” exception.

(3) Appendix B provides additional guidance and examples for determining procedures for evaluating impracticality of applying latest certification specifications to a changed product rule.

(a) The exception of impracticality is a qualitative and/or quantitative cost/safety benefit assessment for which it is difficult to specify clear criteria. Experience to date with applicants has shown that justification of impracticality is more feasible when both applicant and authority agree at an earlier discussion that the effort (in terms of cost, changes in manufacturing, etc.), required to comply would not be

ED Decision 2011/010/R

01/12/2011

commensurate with a small incremental safety gain. This would be clear even without the need to perform any detailed cost/safety benefit analysis (although cost analysis could always be used to support an appropriate amendment level).

Note: The impractical exception should not be based on the size of the applicant’s

company or their financial resources. Costs to comply with a later amendment should be evaluated against the safety benefit of complying with the later amendment. Applicants that may not be able to afford the cost because of reasons such as fewer resources, will not be granted the impractical exception when the cost is comparable to the safety benefit achieved by complying with a later amendment.

(b) For example, a complex redesign of an area of the baseline aircraft may be required to comply with a new certification specification, and that redesign may make the changed product uncommon with respect to design and manufacturing processes from the existing family of derivatives. Relevant service experience of the existing fleet of the baseline aircraft family would be required to show that there has not been a history of problems associated with the hazard that the new amendment in question was meant to address. In this way, the incremental cost/impact to the applicant is onerous and the incremental safety benefit that would be realised by complying with the later amendment would be minimal, and this would be justified with a demonstrated acceptable service experience in relation to the hazard that the new certification specification addresses.

11. Step 8 of Figure 1. Is the Proposed Type-certification Basis Adequate?

a. Regardless of whether the change is significant or not, the applicant’s proposed type-

certification basis may be deemed inadequate – that is, the change includes features or characteristics that were not foreseen during the initial (or previously approved) typecertification. These features or characteristics, if not adequately addressed, may make the product unsafe for the uses for which certification is requested. This would obstruct issuance of the requested approval for the change. The change must comply with later standards (such as, a later amendment or a special condition). An example is adding a flight critical system such as an electronic air data display on Part-25 aeroplane whose existing type-certification basis did not have lightning protection requirements. In this case, compliance with the certification specification for lightning protection will be required, even though this is not a significant change.

b. In cases where inadequate or no airworthiness standards exist for the change in the

proposed type-certification basis, but adequate standards exist in a subsequent amendment of the applicable airworthiness code, the subsequent amendment will be made part of the typecertification basis to assure its adequacy.

c. In cases where no adequate standard exists in any subsequent amendment of the applicable

airworthiness code because of one or more reasons specified in 21A.16B(a), the Agency will prescribe special conditions containing necessary safety standard per 21A.16B(b). 21A.101(d) allows for the application of special conditions, or for changes to the existing special conditions, to address the changed designs where the proposed type-certification basis does not provide adequate standards with respect to the proposed change. Reference section 3 of Chapter 4 for additional information pertaining to special conditions.

ED Decision 2011/010/R

01/12/2011

d. Reserved

e. The final type-certification basis may consist of a combination of the certification

specifications of the applicable airworthiness code at different amendment levels ranging from the original type-certification basis to the most current amendments, and special conditions.

Chapter 4. Other Considerations

1. Design Related Operating Requirements. The use of exceptions under 21A.101 is not

intended to alleviate or preclude compliance with applicable operating rules or directives that prescribe compliance with the applicable additional airworthiness (design-related) specifications for operations.

2. Excepted Products under 21A.101(c)

a. An applicant for a design change to an excepted product may show that the changed

product complies with the existing type-certification basis incorporated by reference in the TC. If the Agency finds that the change is significant “in an area”, the Agency will require compliance with a later amendment to the existing type-certification basis that applies to that affected area and any certification specification the Agency finds is directly related. For excepted products, changes that meet one of the following criteria, in the area of change, are automatically considered significant if:

 The general configuration or the principles of construction are not retained, or

 The assumptions used for certification of the product to be changed do not remain valid.

b. However, the Agency may allow the applicant to comply with an earlier amendment to the

airworthiness code initially designated or with the existing type-certification basis if the Agency agrees to the applicant’s justification.

c. For a design change to an excepted product that contains new features, which are not

covered in the existing type-certification basis, the Agency will designate the applicable certification specifications at the appropriate amendment level, beginning with the existing type-certification basis and progressing to the most appropriate later amendment level for the change. For a change that contains new design features that are novel and unusual for which there are no later applicable certification specifications at a later amendment level, the Agency will designate special conditions per 21.101(d).

d. The exception provided for excepted products under 21A.101(c) applies at the aircraft level

only. Design changes to type-certificated engines and propellers installed on these excepted aircrafts are assessed as separate products using 21A.101(a) and (b).

3. Special Conditions, 21A.101(d). 21A.101(d) allows for the application of special

conditions, or for changes to existing special conditions, to address the changed designs where the proposed type-certification basis does not provide adequate standards for an area, system, part or appliance related to the change and no adequate standard exist in any subsequent amendment of the applicable airworthiness code up to the airworthiness code in effect on the date of the application for the change. The objective is to achieve a level of safety consistent with that provided for other areas, systems, parts or appliances affected by the change by the other certification specifications of the proposed type-certification basis. The application of special conditions to a design change is not, in itself, a reason for it to be classified as either a substantial change or a significant change. When the change is significant with earlier certification specifications allowed through exceptions, or not significant, the level of safety

ED Decision 2011/010/R

01/12/2011

intended by the special conditions should be consistent with the agreed type-certification basis. Note that special conditions may also be applied under 21A.16B when the intended use of the changed product is unconventional or experience from other similar products in service or products having similar design features has shown that unsafe conditions may develop.

4. Effective Period for an Application to Change a Type-Certificate (21A.101(e))

Per 21A.101(e), an application for, or a change to, a TC for large aeroplanes and large rotorcraft is effective for 5 years, and an application for a change to any other TC is effective for 3 years. This is intended to ensure that the type-certification basis for the changed product is as current as practical. According to 21A.101(e) (1) and (2), in a case where the change has not been approved, or it is clear that it will not be approved under the time limit established under this subparagraph, the applicant may:

1. File a new application for a change to the type-certificate and comply with all the provisions of paragraph 21A.101 (a) applicable to an original application for a change; or

2. File for an extension of the original application and comply with the provisions of paragraph (a) for an effective date of application, to be selected by the applicant, not earlier than the date which precedes the date of approval of the change by the time period established under this subparagraph for the original application for the change.

This is consistent with the requirements of 21A.17 for a new TC and defines the process of updating the type-certification basis if these time limits are exceeded.

5. Special purpose aircraft

When a change is proposed to aircraft which is designed or modified for a special purpose to operate in restricted airworthiness category (under a restricted certificate of airworthiness), the process of establishing the type-certification basis of the changed product is in principle the same as for aircraft with a standard certificate of airworthiness. 21A.101 is equally applicable to those special purpose aircraft, except that the applicable certification specifications, the proposed change must comply with, can exclude the paragraphs of the applicable airworthiness code that the Agency finds inappropriate for the special purpose for which the aircraft is to be used and may include possible alternative specifications to address that special purpose. Nevertheless, the “top-down” approach under 21A.101(a) and (b) (and the guidance in Chapter 3 of this GM) generally applies also to special purpose aircraft unless the aircraft is meeting the criteria in 21A.101(c) for excepted products, for which “bottom-up” approach applies (see above section 2 in this Chapter). All the exception routes under 21A.101(b)(1), (2) and (3) are still available, in particular the “not materially contributing to the level of safety” and “impractical” exceptions may be found justifiable considering the intended special purpose of the aircraft.

6. Reserved

7. Documentation. All changes that result in a revision to the product’s type-certification

basis should be reflected on the amended TC or STC. The resulting type-certification basis should be retained as it forms part of the compliance record required by the applicable

Agency’s internal working procedures.

ED Decision 2011/010/R 01/12/2011

The Appendix 1 to GM 21A101 is amended is follows:

Appendix 1A. to GM 21A.101

Classification of Changes

Appendix 1 includes tables of typical changes for small aeroplanes (figure 1), large aeroplanes (figure 2), rotorcraft (figure 3), and engines/propellers (figure 4) that meet the definition of a significant change or substantial change for each product line. The Appendix also includes typical changes that do not achieve the significant level. a) The examples in the tables were developed from data collected from regulatory files and included industry review and input. They clearly are changes that we have seen in the past and will likely continue to see in the future. The Agency has made the determination, based on applying the automatic criteria, that these changes are significant or not significant.

b) The columns “Change to General Configuration”, “Change to Principles of Construction” and “Assumptions of Certification” reflect the automatic criteria of 21A.101(b)(1)(i) and (ii). The “Notes” column provides typical rationales that are considered in evaluating the designation of the criteria. c) The tables may be used in one of two ways:

(i) to classify a proposed change that is listed in the table, or

(ii) in conjunction with the three automatic criteria, to understand the logic used in the table to help classify a proposed change not in the table.

d) The classification may change due to cumulative effects and/or combinations of individual changes.

The following examples of substantial, significant and not significant changes are adopted by the Federal Aviation Administration (FAA), European Aviation Safety Agency (EASA) EASA and Transport Canada Civil Aviation (TCCA) through an international collaboration. The classification may change due to cumulative effects and/or combinations of individual changes. The “N/A” indicated in the substantial example tables indicates “Not Applicable” at the “21A.19 Substantial Evaluation” phase.

ED Decision 2011/010/R

01/12/2011

Figure 1. Table of e Table 1.Examples of Changes for Small Aeroplanes (CS-23)

The following examples are for SUBSTANTIAL changes for Small Aeroplanes (CS-23):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions used general principles of for certification configuration? construction? been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Change in wing Yes N/A No N/A Yes N/A Proposed location change in (tandem, design is so forward, canard, extensive that a high/low). substantially complete investigation of compliance with the applicable regulations is required.

Fixed wing to tilt Yes N/A Yes N/A Yes N/A Proposed wing. change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.

Increase or Yes N/A Yes N/A Yes N/A Proposed decrease in the change in number of design is so engines from extensive that a one to two. substantially complete investigation of compliance with the applicable regulations is required.

Replacement of Yes N/A Yes N/A Yes N/A Proposed piston or turbo- change in prop engines design is so with turbojet or extensive that a turbofan substantially engines. complete investigation of compliance with the applicable regulations is required.

ED Decision 2011/010/R

01/12/2011

The following examples are for SUBSTANTIAL changes for Small Aeroplanes (CS-23):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions used general principles of for certification configuration? construction? been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Change in Yes N/A Yes N/A Yes N/A Proposed change in engine design is so configuration extensive that a (tractor/pusher). substantially complete investigation of compliance with the applicable regulations is required. Increase from Yes N/A No N/A Yes N/A Proposed subsonic to change in design is so supersonic flight extensive that a regime. substantially complete investigation of compliance with the applicable regulations is required.

Change from an No N/A Yes N/A Yes N/A Proposed all metal change in aeroplane to all design is so composite extensive that a primary substantially structure complete (fuselage, wing, investigation of empennage). compliance with the applicable regulations is required.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Conventional Yes No Yes Change in general tail to T-tail or configuration. Y-tail, or vice Requires extensive versa. structural, flying qualities and performance reinvestigation. Requires a new AFM to address performance and flight

characteristics.

Changes in Yes No Yes Change in general wing configuration. configuration Likely requires such as extensive changes (addition of tail to wing structure. strakes or Requires a new change in AFM to address dihedral, performance and changes in flight wing span, flap characteristics. or aileron NOTE: Small span, angle of changes to wingtip incidence of are not significant the tail, changes. See table addition of for not significant winglets, or changes. increase of more than 10 % of the original wing sweep of more than 10% at the quarter chord. Changes to tail Yes No Yes Change in general configuration configuration. such as the Likely requires addition of tail extensive changes strakes or to tail structure. angle of Requires a new incidence of AFM to address the tail. performance and flight characteristics.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Note: Small

changes to tail are not significant changes. Tricycle/tail Yes No No Change in general wheel configuration. undercarriage Likely, at airplane change or level, general addition of configuration floats. Principles of construction and certification assumptions remain valid. Increase in Yes Yes Yes Change in general seating configuration. capacity Change in resulting in a principles of different construction. certification Requires extensive category (e.g., construction refrom normal to assessment. commuter Change in category) certification where assumptions. configuration Requires new AFM or principles of and pilot type construction rating. changes or assumptions do not remain valid. Passenger to Yes No Yes Change in general freighter configuration configuration affecting load conversion paths, aeroelastic which involves characteristics, the aircraft related introduction of systems, etc. a cargo door or Change in design an increase in assumptions. floor loading of more than 20%, or provision for carriage of passengers

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

and freight together.

A fuselage Yes No Yes Likely extensive stretch would changes to be considered fuselage structure, significant if it aerodynamics, would aircraft systems invalidate the performance, and existing operating substantiation, envelope. or would Requires new AFM change the to address primary performance and structure, flight aerodynamics, characteristics. or operating envelope sufficiently to invalidate the assumptions of certification Replace No No Yes Invalidates reciprocating certification engines with assumptions. the same Requires a new number of AFM to address turbo-propeller performance and engines where flight the operating characteristics. envelope is expanded. Addition of a No No Yes Invalidates turbo-charger certification that changes assumptions due the power to changes in envelope, operating envelope operating and limitations. range, or Requires a new limitations. AFM to address performance and flight characteristics. The No Yes Yes Invalidates replacement of certification an engine of assumptions. higher rated Requires a new

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

power or AFM to address increased performance and thrust would flight be considered characteristics. significant if it Likely changes to would primary structure. invalidate the Requires extensive existing construction resubstantiation, investigation. or would change the primary structure, aerodynamics or operating envelope sufficiently to invalidate the assumptions of certification.

A change in No Yes Yes Change in the type of principles of material, such construction and as composites design from in place of conventional metal, or one practices. composite fiber Likely change in material design/certification system with assumptions. another (e.g., carbon for fiberglass), for primary structure would normally be assessed as a significant change.

Change No No Yes Certification involving assumptions appreciable invalidated. increase in Requires a new design speeds AFM to address Vd, Vmo, Vc, performance and or Va. flight characteristics.

Short take-off No No Yes Certification

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

and landing assumptions (STOL) kit. invalidated. Requires a new AFM to address performance and flight characteristics.

A change in No No Yes Certification the rated assumptions power or invalidated. thrust is likely Requires a new to be regarded AFM to address as significant if performance and the design flight speeds are characteristics. thereby changed so that compliance needs to be rejustified with a majority of specifications.

Fuel state: No No Yes Changes in such as design/certification compressed assumptions. gaseous fuels, Extensive or fuel cells. alteration of fuel This could storage and completely handling systems. alter the fuel storage and handling systems and possibly affect the aeroplane structure. A design No No Yes Certification change that assumptions alters the invalidated. aircraft flight Requires a new characteristics AFM to address or performance performance and from the type flight design would characteristics. normally be

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

significant if it appreciably changes the kinematics or dynamics of the airplane aeroplane. Weight No No Yes Certification increase which assumptions places the invalidated. aircraft into Requires new AFM. the commuter category (i.e., above 12500 lbs.)

A change in the No No Yes Changes in design flight control and certification concept for an assumptions. aircraft, for Requires extensive example to fly systems by wire (FBW) architecture and and side-stick integration control, or a reinvestigation. change from Requires a new hydraulic to AFM. electronically actuated flight controls, would in isolation normally be regarded as a significant change. Change to No No Yes An increase aeroplane’s greater than 10 % cabin operating in maximum cabin altitude, or pressure operating differential pressure. invalidates certification assumptions and the fundamental approach used in decompression, structural strength, and fatigue.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Addition of No Yes Yes Extensive airframe cabin changes affecting pressurisation load paths, fatigue system. evaluation, aeroelastic characteristics, etc. Requires extensive construction reinvestigation. Invalidates design assumptions.

Changes in Yes No Yes Emergency egress types and requirements number of exceed those emergency previously exits or an substantiated. increase in Invalidates maximum assumptions of certificated certification. passenger capacity in excess of maximum passenger capacity demonstrated for the aircraft type.

A change in the No No Yes Extensive changes required to avionics and number of flight aircraft systems. crew, which Invalidates necessitates a certification complete assumptions. cockpit re- Requires a new arrangement, AFM. and/or an increase in pilot workload would be a significant change.

An appreciable No No Yes Invalidates Expansion of certification an aircraft’s assumptions. operating Requires new AFM envelope or to address operating performance and

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

capability flight would normally characteristics. be a significant An appreciable change. e.g., expansion of an increase in operating maximum capability would altitude normally be a limitation, significant change approval for (e.g., an increase flight in known in maximum icing altitude limitation, conditions, an approval for flight increase in in known icing airspeed conditions, or an limitations. increase in airspeed limitations). Merely operating a product to an expanded envelope for which it was originally designed is generally not a significant change. In this case, the assumptions used for certification of the basic product remain valid and the results can be applied to cover the changed product with predictable effects or can be demonstrated without significant.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Replacement No No Yes A major change to of an aviation the aeroplane. The gasoline general engine with an configuration and engine of principles of approximately construction will the same usually remain horsepower valid; however, the utilising diesel assumptions for fuel. certification are invalidated.

A major No No Yes Extensive changes Comprehensive to avionics and flight deck electrical systems upgrade, such design. as conversion Invalidates from entirely certification federated, assumptions. independent electro- Extensive remechanical assessments of flight systems instruments to integration, flight highly crew workload, integrated and human factors combined evaluation are electronic required. display Affects avionics systems with and electrical extensive use systems of software integration and and/or architecture complex concepts, or electronic philosophies. hardware.

Introduction of No No Yes Invalidates original auto-land. design assumptions. Conventional Yes No Yes Change in general tail to T-tail or configuration. Requires extensive Y-tail, or vice structural, flying versa qualities and performance re-investigation. Requires new AFM

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

to address performance and flight characteristics.

Airframe life No No Yes This modification extension. pertains to fuselage and/or wing limits, and ageing aeroplane concerns. An increase from the original life limit which constitutes a re-evaluation of certification design assumptions.

Extensive Yes No No Requires extensive structural changes to airframe fuselage structure, modification, affects aircraft such as a large systems, and opening in requires a new fuselage. AFM to address performance and flight characteristics. Fuselage Yes No Yes Cabin interior stretch or changes are shortening in related changes the cabin or since occupant pressure safety vessel. considerations are impacted by a cabin length change. Even if a new cabin interior is not included in the product level change, the functional effect of the fuselage plug has implications on occupant safety (e.g., the dynamic environment in an emergency

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Small Aeroplanes (CS-23):

Description Is there a Is there a Have the Notes of change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

landing, emergency evacuation,

etc.), and thus the existing cabin interior becomes an affected area. Conversion Yes No Yes In many cases this from normal change could be category to considered a commuter substantial change category to the type design. aeroplane. Therefore, a proposed change of this nature would be subject to Agency determination under 21A.19.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Addition of No No No A major change to wingtip the aeroplane. modifications Likely the original (not winglets). general configuration, principles of construction and certification assumptions remain valid.

Installation of No No No Although a major skis or wheel change to the skis. aeroplane, likely the original general configuration, principles of construction and certification assumptions remain valid.

FLIR or No No No Additional flight or surveillance structural camera evaluation may be installation. necessary, but the change does not alter basic aeroplane certification.

Litter, berth and No No No Not an airplane cargo tie down level change. device installation.

Increased tire No No No Not an airplane size, including level change. tundra tires.

Replacement of No No No Although a major one propeller change to the type with airplane another aeroplane, likely (irrespective of the original increase in general number of configuration, blades). principles of construction and

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

certification assumptions remain valid. Addition of a No No No Not an airplane turbo-charger level change. that does not change the power envelope, operating range, or limitations (e.g. a turbonormalised engine, where the additional power is used to enhance high altitude or hot day performance). Replace a petrol No No No Although a major engine with a change to the diesel engine or airplane, likely the approximately original general the same configuration, horsepower. principles of construction and certification assumptions remain valid. Substitution of No No No Not an airplane one method of level change. bonding for another (e.g. change in type of adhesive). Substitution of No No No Not an airplane one type of level change. metal for another. Any change in No No No Not an airplane construction or level change. fastening not involving primary structure. A new fabric No No No Not an airplane type for fabric level change.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

skinned aircraft. Increase in flap No No No Although a major speed or change to the undercarriage airplane limit speed. aeroplane, likely the original general configuration, principles of construction, and certification assumptions remain valid. Structural No No No Although a major strength change to the increases airplane aeroplane, likely the original general configuration, principles of construction, and certification assumptions remain valid.

Instrument flight No No No Not an airplane rules (IFR) level change. upgrades involving installation of components (where the original certification does not indicate that the aeroplane is not suitable as an IFR platform, e.g. special handling concerns).

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Fuel lines, where No No No Not an airplane engine level change. horsepower is increased but fuel flow is not increased beyond the certificated maximum amount.

Fuel tanks, No No No Not an airplane where fuel is level change. changed from gasoline to diesel fuel and tank support loads are small enough that an extrapolation from the previous analysis would be valid. Chemical compatibility would have to be substantiated. Limited changes No No No Although a major in a change to the pressurisation aeroplane, likely system, e.g. the original number of general outflow valves, configuration, type of principles of controller or size construction, and of pressurised certification compartment, assumptions but the system remain valid. must be resubstantiated if the original test data are invalidated.

Install a quieter No No No Not an airplane exhaust system. level change.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Changes in No No No Not an airplane engine cooling level change. or cowling.

Changing fuels No No No Although a major of substantially change to the the same type: aeroplane, likely such as AvGas the original to AutoGas, general AvGas (80/87) configuration, to AvGas principles of (100LL), ethanol construction, and to isopropyl certification alcohol, Jet B to assumptions Jet A (although remain valid. Jet A to Jet B may be considered significant due to the fact that Jet B is considered potentially more explosive). Fuels that No No No Although a major specify different change to the levels of aeroplane, likely “conventional” the original fuel additives general that do not configuration, change the principles of primary fuel construction, and type. Different certification additives (MTBE, assumptions ETBE, ethanol, remain valid. amines, etc.), in AvGas would not be considered a significant change. A change to the No No No Although a major maximum take- change to the off weight of less aeroplane, likely than 5%, unless the original assumptions general made in configuration, justification of principles of

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

the design are construction, and thereby certification invalidated. assumptions remain valid. (Unless this weight increase would result in a shift to commuter

category.)

An additional No No No Although a major aileron tab (e.g., change to the on the other aeroplane, likely wing). the original general configuration, principles of construction, and certification assumptions remain valid. Larger diameter No No No Not an airplane flight control level change. cables with no change in routing, or other system design. Autopilot No No No Although a major installation (for change to the instrument flight aeroplane, likely rules (IFR) use, the original where the general original configuration, certification does principles of not indicate that construction, and the aeroplane is certification not suitable as assumptions an IFR remain valid. platform). Increased No No No Not an airplane battery capacity level change. or relocate battery. Replace No No No Not an airplane generator with level change. alternator. Additional No No No Not an airplane lighting (e.g. level change.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

navigation lights, strobes). Higher capacity No No No Not an airplane brake level change. assemblies. Increase in fuel No No No Not an airoplane tank capacity. level change, unless it is tied with an increase in gross weight. Addition of an No No No oxygen system. Relocation of a No No No galley.

Passenger to No No No Although a major freight (only) change to the conversion with aeroplane, likely no change to the original basic fuselage general structure. configuration, principles of construction, and certification assumptions remain valid. Requires certification substantiation applicable to freighter requirements.

New cabin No No No interior with no fuselage length change.

Installation of No No No Not an airplane new seat belt or level change. shoulder harness.

A small increase No No No At a airplane in cg range. product level, no change in general configuration, principles of construction, and

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Small Aeroplanes (CS-23): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

certification assumptions.

APU installation No No No Although Aa that is not flight major change to essential the aeroplane level, likely the original general configuration, principles of construction, and certification assumptions remain valid. Requires certification substantiation applicable to APU installation requirements.

An alternative No No No Not an airplane auto-pilot. level change.

Addition of Class No No No Not an airplane B Terrain level change. Awareness and Warning Systems (TAWS).

ED Decision 2011/010/R

01/12/2011

Figure 2. Table 2. Examples of changes for Large Aeroplanes (CS-25)

The following examples are for SUBSTANTIAL changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Change in the Yes N/A No N/A Yes N/A Proposed change number or in design is so location of extensive that a engines, e.g. substantially four to two wing- complete mounted engines investigation of or two wing- compliance with mounted to two the applicable body-mounted regulations is engines. required.

Change from a Yes N/A No N/A Yes N/A Proposed change high-wing to in design is so low-wing extensive that a configuration. substantially complete investigation of compliance with the applicable regulations is required.

Change from an Yes N/A Yes N/A Yes N/A Proposed change all-metal in design is so aeroplane to all extensive that a composite substantially primary complete structure investigation of (fuselage, wing compliance with and the applicable empennage). regulations is required.

Change of N/A N/A N/A Proposed change empennage in design is so configuration for extensive that a larger substantially aeroplanes complete (cruciform vs. ‘T’ investigation of or ‘V’ tail). compliance with the applicable regulations is required.

Increase from N/A N/A N/A Proposed change subsonic to in design is so supersonic flight extensive that a regime. substantially

ED Decision 2011/010/R

01/12/2011

The following examples are for SUBSTANTIAL changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

complete investigation of compliance with the applicable regulations is required.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Derivative model, Yes Yes Yes Multiple e.g., increased changes passenger payload, packaged into a freighter version or new model. complete update of Increased a certified payload new aeroplane. freighter would change the general configuration and assumptions. Updated aeroplane could change principles of

construction.

Reduction in the Yes No No Extensive number of flight changes to crew (in avionics and conjunction with aircraft flight deck update). systems. Impact to crew workload and human factors, pilot type rating. Modify an aeroplane Yes No Yes New aircraft for flight in known operating icing conditions by envelope. adding systems for Requires major ice detection and new systems elimination. installation and aircraft evaluation. Operating envelope changed. Conversion – Yes No Yes Extensive passenger or airframe combination changes freighter/passenger affecting load to all freighter, paths, including cargo aeroelastic door, redesign floor characteristics,

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

structure and 9g aircraft related net or rigid barrier. systems for fire protection, etc. Design assumptions changed from passenger to freighter. Change to No No Yes Essentially a repressurized cabin certification of including the airframe and introduction of a systems pressurization associated with system. operating envelope Increase in cabin change. pressurisation system. Typically, a change greater than 10 % in operational cabin pressure differential. May require extensive airframe changes affecting load paths, fatigue evaluation, aeroelastic characteristics, etc. Invalidates design assumptions. Addition of leading Yes No No Requires edge slats. extensive changes to wing structure, adds aircraft systems, and requires a new aeroplane flight manual AFM to address performance and flight characteristics.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Fuselage length Yes No No Requires change – lengthen extensive or shorten fuselage changes to stretch or fuselage shortening in the structure, cabin or pressure affects aircraft vessel. level systems, and requires a new aeroplane flight manual to address performance and flight characteristics.

Cabin interior changes are related changes since occupant safety considerations are impacted by a cabin length change. Even if a new cabin interior is not included in the product level change, the functional effect of the fuselage plug has implications on occupant safety (e.g., the dynamic environment in an emergency landing, emergency evacuation, etc.), and thus the cabin interior becomes an affected area.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Extensive Yes No No Requires structural airframe extensive modification, such changes to as installation of a fuselage large telescope structure, with large opening affects aircraft in fuselage. systems, and requires a new AFM to address performance and flight characteristics.

Changing the Yes No No Requires number of axles or extensive number of landing changes to gear done in aircraft context with a structure, product change affects aircraft that involves systems, and changing the requires AFM aeroplane gross changes. weight.

Primary structure No Yes No Change in changes from principles of metallic material to construction composite and design material. from conventional practices. This Airframe life No No Yes extension. modification pertains to fuselage and/or wing limits, and ageing aeroplane concerns. An increase from the original life limit which constitutes a re-evaluation of certification design assumptions.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Typically, an No No Yes When it rRequires increase in extensive redesign weight of substantiation of more than 10%. aircraft structure, aircraft (Note: performance and Potentially flying qualities substantial if it is and associated a change from a systems. high wing to a low wing, or a new wing.)

Installation of Yes No Yes winglets.

Wing changes in Yes No No Yes When it requires span, sweep, tip extensive changes designs or wing to wing structure, chord. adds aircraft systems, and requires a new aeroplane flight manual AFM to address performance and flight characteristics. (NOTE: Potentially substantial if it is a change from a high wing to a low wing, or a new wing.)

Change in type or NoYes No Yes The new number of emergency egress emergency exits requirements in conjunction exceed those with or an previously increase in the substantiated. maximum certificated number of passengers.

Comprehensive No No Yes Affects avionics

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

flight deck and electrical

upgrade, such as systems

conversion from integration and

entirely architecture

federated, concepts and

independent philosophies.

electro- This drives a remechanical flight assessment of instruments to flight crew highly integrated workload and and combined other human electronic factors issues, display systems and requires a rewith extensive evaluation of the use of software original design and possibly assumptions used complex for the cockpit. hardware.

Change in YesNo No Yes When the degree

primary flight of change is so

controls to fly by extensive that it

wire (FBW) affects basic

system. aircraft systems

integration and (Some architecture aeroplanes have concepts and some degree of philosophies. This FBW. Achieving drives a complete full FBW may be reassessment of a not significant flight crew change on some workload, handling aeroplanes.) qualities, and

performance

evaluation, which

are different from

the original design

assumptions.

Replace Yes No No Requires

reciprocating extensive changes

with turbo- to airframe

propeller structure, addition

engines. of aircraft

systems, and a

new aeroplane

flight manual AFM

to address

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

performance and flight characteristics.

Typically a No No Yes When it rRequires thrust increase re-substantiation of more than of powerplant 10 %. installation, and has a marked affect on aircraft performance and flying qualities.

Initial No No Yes Baseline installation of an aeroplane not auto-land designed for autosystem. land operation, potential crew workload and systems compatibility issues.

Installation of a No No Yes Requires changes new fuel tank, to airframe, (horizontal systems and AFM. stabiliser tank or Results in auxiliary fuel performance tank in the changes. fuselage outside the wing in conjunction with increased maximum takeoff weight and takeoff thrust).

Main deck cargo Yes No No Redistribution of door installation. internal loads, change in aeroelastic characteristics, system changes. No No Yes Expansion of an An expansion of aircraft’s operating operating capability would envelope. normally be a significant change (e.g. an increase

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

in maximum altitude limitation, approval for flight in known icing conditions, or an increase in airspeed limitations). Merely operating a product to an expanded envelope for which it was originally designed is generally not a significant change. In this case, the assumptions used for certification of the basic product remain valid and the results can be applied to cover the changed product with predictable effects or can be demonstrated without significant physical changes to the product. Conversion from No No Yes Completely new a passenger floor loading and floor to a cargo design. floor and Redistribution of installation of a internal loads, cargo handling change in cabin system. safety requirements, system changes.

Initial No No Yes Changes installation of an emergency APU essential for electrical power aircraft flight requirements, change in flight

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

operation. manual AFM and operating characteristics. Assumptions of Conversion from No No Yes hydraulically certification for actuated brakes aeroplane performance are to electrically changed. actuated brakes. An increase Change to No No Yes aeroplane’s greater than 10 % cabin operating in maximum cabin pressure altitude, or differential operating invalidates

pressure.

certification assumptions and the fundamental approach used in decompression. structural strength, and fatigue analysis. Installation of Yes No Yes engine thrust reversers.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 1A.101(b)(1)(ii)

Alternate engine No No No Although an installation or aeroplane level hush kit at same change, Typically, it is position. not significant any longer as there is not more than a 10% increase in thrust or a change in the principles of propulsion.

A small change in No No No A small change in Ffuselage length fuselage length due change – to re-fairing the aft lengthen or body or radome fFor shorten fuselage cruise performance due to refairing reasons, where such the aft body or changes do not radome. require extensive structural, systems, aerodynamic, or AFM changes.

Refairing of wing No No No Does not require tip caps (e.g. for extensive structural, lights, fuel dump AFM, or systems pipes) and changes. addition of splitter plates to the trailing edge thickness of the cruise airfoil.

Additional power No No No Usually no change in used to enhance basic operating high altitude or envelope. Existing hot day certification data can performance. be extrapolated. Could be significant product change if the additional power is provided by installation of a rocket motor or additional, on demand engine due to changes in certification assumptions.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 1A.101(b)(1)(ii)

General avionics No No No These modifications changes. are generally adaptive* in nature, and do not change the original certification assumptions, alter basic cockpit design architecture concepts and philosophies, and do not have a major impact on crew workload or man/machine. *Adaptive means the change adapts to the existing airplane buses, power, structure, …

Installation of an No No No See note It may be possible auto-pilot system. that the Mmodification is generally adaptive in nature, with no change to original certification assumptions. However, in certain cases the installation of an auto-pilot may include extensive changes and design features which change the assumptions for certification (i.e. installation of the auto-pilot may introduce a number of additional mechanical and electronic failure modes and change the hazard classification of given aircraft level failures).

Integrated No No No The basic modular avionics functionality of the

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 1A.101(b)(1)(ii)

systems are unchanged. No change from analog to digital.

Installation or No No No Special conditions rearrangement of could be used for new an interior in an and novel features aircraft.

Change from No No No Method of assembled construction must be primary structure well understood. to monolithic or integrally machined structure.

Modification to ice No No No Recertification protection required, but systems. certification basis is adequate.

Brakes: design or No No No Recertification material change, required, but e.g. steel to certification basis is carbon. adequate.

Redesign floor No No No By itself, not a structure. significant product level change. It could be a is significant if part of a cargo conversion of a passenger aeroplane.

New cabin interior No No No A new cabin interior with no fuselage includes new ceiling length change. and sidewall panels, stowage, galleys, lavatories, and seats. New and novel features in the cabin interior may require special conditions. Many interior related requirements are incorporated in operational rules. Even though the design approval

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Large Aeroplanes (CS-25):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 1A.101(b)(1)(ii)

holder may not be required to comply with these requirements, the operator may be required to comply.

A re-arrangement No No No Re-arrangement of an interior requires the use of (e.g. seats, the existing floor galleys, mounting structure. lavatories, closets, etc)

Novel or unusual No No No The component method of change does not rise construction of a to the product level. component. Special conditions could be required if there are no existing specifications that adequately address these features.

Initial installation No No No A stand-alone initial of a non-essential APU installation on an APU. airplane aeroplane originally designed to use ground/airport supplied electricity, and air-conditioning. In this case, the APU would be an option to be independent of airport power.

Figure 3. Table of examples of Changes for Rotorcraft

The following are examples of substantial changes:

ED Decision 2011/010/R

01/12/2011

Table 3. Examples of Changes for Rotorcraft (CS-27 and 29)

The following examples are for SUBSTANTIAL changes for Rotorcraft (CS-27 and CS-29): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Change from the Yes N/A No N/A Yes N/A Proposed change in number and/or design is so configuration of extensive that a rotors (e.g. substantially main & tail rotor complete system to two investigation of main rotors). compliance with the applicable regulations is required.

Change from an Yes N/A Yes N/A Yes N/A Proposed change in all metal design is so rotorcraft to all extensive that a composite substantially rotorcraft. complete investigation of compliance with the applicable regulations is required.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Comprehensive Yes No No Yes The degree of flight deck change is so upgrade, such as extensive that it conversion from aAffects avionics and entirely electrical systems federated, integration and independent architecture electro- concepts and mechanical flight philosophies. instruments to This drives a highly integrated complete and combined reassessment of electronic display flight crew workload systems with and other human extensive use of factor issues, and software and/or requires a recomplex evaluation of the electronic original design hardware. assumptions used for the cockpit.

Certification for No No Yes flight into known icing conditions.

(Fixed) flying Yes No Yes No Yes This drives a controls from complete mechanical to fly reassessment of the by wire. rotorcraft controllability and flight control failure.

Addition of an Yes No Yes Yes May be a substantial engine, e.g. from change depending single to twin or upon project details. reduction of the number of engines, e.g., from twin to single.

A change of rotor drive system No Yes Yes primary gearbox splash type lubrication system to a pressure lubricated system due to an

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

increase in horsepower of an engine or changing a piston engine to a turbine engine.

A fuselage or tail Yes No Yes boom modification that changes the primary structure, aerodynamics, or and operating envelope sufficiently to invalidate the certification assumptions. Application of an No Yes Yes approved primary structure to a different approved model (e.g. installation on a former model of the main rotor approved on a new model that results in increased performance). Extensive primary No Yes Yes Change in principles structure changes of construction and from metallic assumptions used material to for certification for composite the product level material. change. Changes of a few individual elements from metal to composite are not typically considered a significant change. Emergency No No Yes Any Many EMS Medical Service configurations will (EMS) not be classified as configuration with significant. primary structural Modifications made

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

changes sufficient for EMS are typically to invalidate the internal, and the certification general external assumptions. configuration is normally not affected. These changes should not automatically be classified as significant. Skid landing gear Yes No Yes If the rotorcraft is to wheel landing such that the skid or gear or wheel wheel configuration landing to skid. is inherent in the basic certification design, the change may be not significant. Change of the Yes No No Yes The number of rotor addition/deletion of blades. rotor blades may not be significant provided the remainder of the basic propulsion system remains essentially unchanged. Change tail anti- Yes Yes No torque device (e.g. tail rotor, ducted fan or other technology).

Passenger Yes No Yes Depends on the fire configured fighting helicopter to a fire configuration. fighting equipment configured helicopter.

Passenger Yes No Yes Depends on the configured agricultural helicopter to an configuration. agricultural configured helicopter.

ED Decision 2011/010/R

01/12/2011

The following examples are for SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

A new Category A No No Yes certification approval to an existing configuration.

Instrument Flight No No Yes Rules (IFR) upgrades involving installation of upgraded components for new IFR configuration.

Human External No No Yes Must comply with Cargo (HEC) the latest HEC certification Certification approval. specifications in order to obtain operational approval. HEC include fatigue, Quick Release Systems, HIRF, OEI performance and OEI procedures.

Reducing the No No Yes Significant change, if number of pilots there are extensive for IFR from 2 to equipment and 1. design changes such that the certification assumptions are invalidated.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Emergency floats No No No Must comply with the specific applicable specifications for emergency floats. This installation, in itself, does not change the rotorcraft configuration, overall performance or operational capability. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, or flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the typecertificated product level.

FLIR or surveillance No No No Additional flight or camera installation structural evaluation may be necessary but the change does not alter the basic rotorcraft certification.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Helicopter Terrain No No No Certificated per Awareness Warning rotorcraft HTAWS System (HTAWS) AC guidance for operational material and FAA credit. TSO-C194.

Health Usage No No No Certificated per Monitoring System rotorcraft HUMS (HUMS) for AC guidance Maintenance Credit. material.

Expanded limitations No No No Expanding an with minimal or no operating envelope design changes, (such as operating following further altitude and tests/justifications or temperature) and different mix of mission profile limitations (CG (such as passenger limits, oil carrying operations temperatures, to external load altitude, minimum/ operations, or flight maximum weight, over water, or minimum/maximum operations in snow external conditions) are not temperatures, by themselves so speed, ratings different that the structure). original certification assumptions are no longer valid at the type-certificated product level. Installation of a No No No Refer to AC 27-1 new engine type, or AC 29-2 for equivalent to the guidance former one; leaving aircraft installation and limitations substantially unchanged.

Windscreen No No No Does not change installation the rotorcraft overall product configuration.

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Snow skis, “Bear No No No Must comply with Paws” specific certification specifications associated with the change. Expanding an operating envelope (such as operating altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, or flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the typecertificated product level.

External cargo hoist No No No Must comply with the specific applicable requirements for external loads. This installation, in itself, does not change the rotorcraft configuration, overall performance or operational capability. Expanding an operating envelope (such as operating

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

altitude and temperature) and mission profile (such as passenger carrying operations to external load operations, excluding HEC, or flight over water, or operations in snow conditions) are not by themselves so different that the original certification assumptions are no longer valid at the type-certificated product level.

Instrument flight No No No Not a rotorcraft rules (IFR) level change. upgrades involving installation of upgraded components (where the original certification does not indicate that the rotorcraft is not suitable as an IFR platform, e.g., special handling concerns) to replace existing components.

An upgrade to CAT No No No Typically these are A certification engine and drive approval systems rating changes appropriate for CAT A and rotorcraft performance requirements. Rotorcraft modifications, if any necessary, do not typically

ED Decision 2011/010/R

01/12/2011

The following examples are for NOT SIGNIFICANT changes for Rotorcraft (CS-27 and CS-29):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

invalidate the certification assumptions, or change the general configuration of principles of construction.

Figure 4. Engines and Propellers

The following are examples of significant changes:

Turbine engines

ED Decision 2011/010/R

01/12/2011

Table 4. Examples for Engines (CS-E)

The following are examples of SUBSTANTIAL changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Turbine Engines

Traditional turbofan N/A N/A N/A Proposed to geared-fan change in engine. design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.

Note: There

may be certain circumstances where this change would be significant.

Low by-pass ratio N/A N/A N/A Proposed engine to high by- change in pass ratio engine design is so with an increased extensive that a inlet area. substantially complete investigation of compliance with the applicable regulations is required.

Note: There

may be certain circumstances where this change would be significant.

ED Decision 2011/010/R

01/12/2011

The following are examples of SUBSTANTIAL changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

Turbojet to N/A N/A N/A Change in Turbofan. general configuration. Likely change in model designation. Not interchangeable. Assumptions for certification may no longer be valid in terms of lifting, ingestion, icing, blade out criteria etc. Note that this change is most likely substantial under 21A.19.

Turbo-shaft to N/A N/A N/A Proposed turbo-propeller. change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.

Note: There

may be certain circumstances where this change would be significant.

Conventional N/A N/A N/A Proposed ducted fan to change in unducted fan. design is so extensive that a substantially complete investigation of

ED Decision 2011/010/R

01/12/2011

The following are examples of SUBSTANTIAL changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

compliance with the applicable regulations is required.

Note: There

may be certain circumstances where this change would be significant.

Conventional NA NA NA Proposed Turbine engine for change in subsonic operation design is so to afterburning extensive that a engine for substantially supersonic complete operation investigation of compliance with the applicable regulations is required.

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

Turbine Engines

Traditional turbofan Yes No Yes This change to geared-fan would affect the engine. engine in terms of foreign object ingestion (FOD), containment etc.

Note that this change is most likely substantial under 21A.19.

Low by-pass ratio Yes No Yes Change in engine to high by- general pass ratio engine configuration. with an increased Likely change in inlet area. model designation. Not interchangeable Assumptions for certification may no longer be valid in terms of ingestion, icing etc. Note that this change is most likely substantial under 21A.19.

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

Turbojet to Yes No Yes Change in Turbofan general configuration. Likely change in model designation. Not interchangeable Assumptions for certification may no longer be valid in terms of lifting, ingestion, icing, blade out criteria etc. Note that this change is most likely substantial under 21A.19.

Turbo-shaft to Yes No Yes Change in turbo-propeller configuration such as an additional gearbox. Change in model designation. Change in mission profile.

Assumptions for certification may no longer be valid in terms of flight envelope, ratings etc. Note that this change is most likely substantial under 21A.19.

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

Conventional Yes Yes Yes Change in ducted fan to configuration. unducted fan. Change in type. Not interchangeable Assumptions for certification may no longer be valid.

Note that this change is most likely substantial

under 21A.19.

Conventional Change in Yes Yes Yes engine for subsonic configuration operation to after- Change in Type burning engine for supersonic Not operation interchangeable Assumptions for certification may no longer be valid Change in operating envelope Note that this change is l most likely substantial under 21A.19

Increase/decrease NoYes No Yes Change is in the number of associated with compressor/turbine other changes stages with to the ratings resultant change in and operating approved limitations; operational engine dynamic limitations* behaviour, in (*exclude life terms of limits) backbone bending, torque spike effects on casing, surge

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

and stall characteristics, etc.

New design fan Yes No Yes Likely change in blade and fan hub, model or a bladed fan designation disk to a blisk, or a Change is fan diameter associated with change, that could other changes not be retrofitted. that would affect to the engine thrust, ratings and /power operating limitations and have effect affected the engine dynamic behaviour of the engine in terms of backbone bending, torque spike effects on casing, foreign object ingestion behaviour, burst model protection for the aircraft. If there is a diameter change, installation will be also affected. Hydro-Mechanical Yes Yes No YesNo Change in control to engine control FADEC/EEC without configuration. hydro mechanical Likely change in back-up. model designation Not interchangeable Likely fundamental

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

change to engine operation. Assumptions used for certification are no longer valid or were not A change in the No Yes No Change in containment case methods of from hard-wall to construction composite that have construction or vice affected versa, that could inherent not be retrofitted strength, without additional backbone major changes to bending, blade the engine or to case restricting the clearance initial limitations or retention, restrictions in the containment initial installation wave effect on manual. installation, effect on burst model, torque spike effects. Replace gas No No Yes Change is generator (core, associated with turbine/compressor other changes /combustor) with a that would different one that affect engine is associated with thrust/power changes in and have approved affected the operational dynamic limitations*. behaviour of *Exclude life limits. the engine. Assumptions used for certification may no longer be valid.

Piston Engines

Convert from Yes Yes No Change in Mechanical to engine Electronic Control configuration: System. Installation

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

interface of engine changed. Changes to principles of construction: digital controllers and sensors require new construction techniques and environmental testing.

Add Turbocharger Yes No Yes Change in that increases general performance and configuration: changes in overall Installation product. interface of engine changed (exhaust system). Certification assumptions invalidated.: Change in engine configuration Change in operating envelope and performance. Convert from air Yes No Yes Change to cooled cylinders to general liquid cooled configuration: cylinders. Installation interface of engine changed (cooling lines from radiator, change to cooling baffles). Certification assumptions invalidated.: Change in

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Engines (CS-E):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

operating envelope and engine temperature requirements.

Convert from spark- Yes No Yes Change in ignition to general compression- configuration: ignition. installation interface of engine changed (no mixture lever). Certification assumptions invalidated: change in operating envelope and performance.

ED Decision 2011/010/R

01/12/2011

The following are examples of NOT SIGNIFICANT changes for Engines (CS-E): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Turbine Engines

Change in the No No No No change in material from one performance. type of metal to No likely change in another type of model designation metal of a compressor drum. Assumptions are still valid.

Increase/decrease No No No No change in in the number of performance. compressor/turbine Model designation stages without may or may not resultant change in change operational performance Assumptions are envelope. still valid.

New components No No No No change in internal to the configuration. FADEC/EEC the Retrofitable. introduction of which does not Assumptions used change the function for certification of the system. are still valid. Possible changes in principles of construction are insignificant.

Software changes No No No Rub-strip design No No No Component Level changes Change

A new combustor No No No Component Level that does not Change change the approved limitations, or dynamic behaviour* *exclude life limits.

Bearing changes No No No Component Level

Change

New blade designs No No No Component Level with similar Change material that can

ED Decision 2011/010/R

01/12/2011

The following are examples of NOT SIGNIFICANT changes for Engines (CS-E): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

be retrofitted.

Fan blade redesign No No No Component Level that can be Change retrofitted.

Oil tank redesign No No No Component Level

Change

Change from one No No No Component Level hydro-mechanical Change control to another hydro-mechanical control.

Change to limits on No No No Component Level life limited Change components.

Changes to limits No No No on exhaust gas temperature.

Changes in No No No certification maintenance requirements (CMR) with no configuration changes.

Bump ratings within No No No the product’s physical capabilities that may be enhanced with gas path changes such as blade restaggered, cooling hole patterns, blade coating changes, etc.

ED Decision 2011/010/R

01/12/2011

The following are examples of NOT SIGNIFICANT changes for Engines (CS-E): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

A change in principal No No No Component Level physical properties Change and mechanics of load transfer of a material of primary structure or highly loaded components. For example, change from traditional metal to either an exotic alloy or a composite material on a highly loaded component.

Piston Engine

A change in principal No No No Component Level physical properties Change and mechanics of load transfer of a material of primary structure or highly loaded components. For example, change from traditional metal to either an exotic alloy or a composite material on a highly loaded component. New or redesigned No No No cylinder head, or valves, or pistons.

Changes in No No No Component Level crankshaft. Change

Changes in No No No Component Level crankcase. Change

Changes in No No No Component Level carburettor Change

Changes in No No No No controversy-No mechanical fuel comments injection system.

Changes in No No No mechanical fuel injection pump.

ED Decision 2011/010/R

01/12/2011

The following are examples of NOT SIGNIFICANT changes for Engines (CS-E): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Engine model No No No change to accommodate new aeroplane installation. No change in principles of operation of major subsystems; no significant expansion in power or operating envelopes or in limitations.

No change in basic No No No principles of operation, or a simple mechanical change. For example, change from dual magneto to two single magnetos on a model. Subsystem change No No No produces no changes in base engine input parameters, and previous analysis can be reliably extended. For example, a change in turbocharger where induction system inlet conditions remain unchanged, or if changed, the effects can be reliably extrapolated.

ED Decision 2011/010/R

01/12/2011

The following are examples of NOT SIGNIFICANT changes for Engines (CS-E): Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Change in material No No No Component level of secondary change structure or not highly loaded component. For example, a change from metal to composite material in a non-highly loaded component, such as an oil pan that is not used as a mount pad.

Change in material No No No Component level that retains the change physical properties and mechanics of load transfer. For example, a change in trace elements in a metal casting for ease of pouring or to update to a newer or more readily available alloy with similar mechanical properties.

ED Decision 2011/010/R

01/12/2011

Table 5. Examples of Changes for Propellers (CS-P)

The following are examples of SUBSTANTIAL changes for Propellers (CS-P):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(i) 21A.101(b)(1)(i) 21A.101(b)(1)(ii)

Change in the N/A N/A N/A Proposed number of blades. change in design is so extensive that a substantially complete investigation of compliance with the applicable regulations is required.

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Propellers (CS-P):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

Requires Principle of pitch Yes Yes Yes change such as a extensive change from single modification of the pitch acting to dual change system acting. with the introduction of back-up systems. The inherent control system requires reevaluation.

Introduction of a Yes Yes No Change in propeller different principle of blade retention configuration such as a single Likely change in model row to a dual row designation bearing. Propeller’s operating characteristics and inherent strength require re-evaluation. Requires extensive modification of the propeller hub and blade structure. The inherent strength requires reevaluation. A hub configuration Yes Yes No Requires extensive change such as a modification of split hub to a onepiece hub. the propeller hub structure. The inherent strength requires reevaluation. Changing the Yes Yes No Requires method of extensive modification of mounting the

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Propellers (CS-P):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

propeller to the the propeller engine such as a hub structure. spline to a flange Note: Such a mount. change could be considered not significant if implemented without a change in general configuration or principals of construction. Change in hub Yes Yes No Requires extensive material from steel modification of to aluminium. the propeller hub structure and change to method of blade retention. The inherent strength requires reevaluation. Requires Change in blade Yes Yes Yes material from extensive metal to modification of the propeller composite. blade structure and change to method of blade retention. Composite construction methods required. The inherent strength requires reevaluation. Change from Yes Yes Yes Electronic manufacturing hydro-mechanical and design to electronic control. methods required. Assumptions used for

ED Decision 2011/010/R

01/12/2011

The following are examples of SIGNIFICANT changes for Propellers (CS-P):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

certification are no longer valid or were not addressed in the original certification, i.e., high intensity radio frequency (HIRF) and lightning protection, fault tolerance, software certification and other aspects. The propeller will require special conditions under 21A.16B.

ED Decision 2011/010/R

01/12/2011

The following are examples of NOT SIGNIFICANT changes for Propellers (CS-P):

Description of Is there a Is there a Have the Notes change change to the change to the assumptions general principles of used for configuration? construction? certification been invalidated? 21A.101(b)(1)(ii) 21A.101(b)(1)(i) 21A.101(b)(1)(i)

Change in the No No No Component material of a blade Level Change bearing.

Change to a No No No Component Level Change component in the control system.

Change to a No No No Component propeller de-icer Level Change boot. Changes to the No No No Propeller's operational design operating characteristics envelope such as and inherent an increase in power. strength require re-evaluation. Change to the No No No Propeller's operating intended usage characteristics such as normal to and inherent acrobatic category. strength require re-evaluation.

ED Decision 2011/010/R

01/12/2011

The Appendix 2 to GM 21A101 is replaced by Appendix B as follows:

Appendix 2B to GM 21A.101 PROCEDURE FOR EVALUATING IMPRACTICALITY OF APPLYING LATEST CERTIFICATION SPECIFICATIONS TO A CHANGED PRODUCT

1. Introduction

a. The basic principle of enhancing the level of safety of changed aeronautical products is to

apply the latest certification specifications for significant design changes to the greatest extent practical. In certain cases, the cost of complying fully with a later certification specification may not be commensurate with the small safety benefit achieved. It is recognised that the existing fleet and newly produced aeroplanes, engines and propellers are safe, and any unsafe condition is immediately addressed through the airworthiness directive process. These factors form the basis where compliance with the latest certification specification may be considered impractical, thereby allowing compliance with an earlier certification specification. This appendix gives one method of determining if compliance with a later requirement standard is impractical; however, this does not preclude the use of other methods for improving the safety of aeronautical products.

b. This GM recognises that other procedures can be used and have historically been accepted

on a case-by-case basis. The acceptance of results through the use of these procedures may vary from State to State. Consequently, they may not be accepted through all bilateral certification processes. Regardless of which method is used, the process should show that a proposed type-certification basis is able to achieve a positive safety benefit for the overall product.

c. In this regard, any method used should encourage incorporating safety enhancements that

will have the most dramatic impact on the level of safety of the aircraft while considering effective use of resources. This important point is illustrated graphically in the accompanying figure. This figure notionally shows the interrelation between the total resources required for incorporating each potential safety enhancement with the corresponding net increase in safety benefit.

ED Decision 2011/010/R

01/12/2011

Figure 2. Safety Benefits vs. Resources

d. Typically, one will find that there are proposals that can achieve a positive safety benefit

and that are resource effective. Conversely, there are proposals that may achieve a small safety benefit at the expense of a large amount of resources to implement. Clearly, there will be a point where a large percentage of the potential safety benefit can be achieved with a reasonable expenditure of resources. The focus of the methods used should be to determine the most appropriate standards relative to the respective cost to reach this point.

e. This Appendix to GM 21A.101 provides procedural guidance for determining the practicality

of applying a certification specification at a particular amendment level to a changed product. This guidance can be used to evaluate the safety benefit and resource impact of implementing the latest airworthiness certification specifications in the type-certification basis of a changed product. The procedure is generic in nature and describes the steps and necessary inputs that any applicant can use on any project to develop a position.

f. The procedure is intended to be used, along with good engineering judgment, to evaluate

the relative merits of a changed product complying with the latest certification specifications. It provides a means, but not the only means, for an applicant to present its position in regard to impracticality.

g. The type-certification basis for a change to a product will not be at an amendment level

earlier than the existing type-certification basis. Therefore, when determining the impracticality of applying a certification specification at the latest amendment level, only the increase in safety benefits and costs beyond compliance with the existing type-certification basis should be considered.

2. Procedure for Evaluating Impracticality of Applying Latest Certification Specifications to a Changed Product

The following are steps to determine the impracticality of applying a certification specification at a particular amendment level. The first step will be to identify the regulatory change being evaluated.

a. Step 1: Identify the Regulatory Change Being Evaluated.

In this step, it will be necessary to document:

ED Decision 2011/010/R 01/12/2011

(1) The specific certification specification (for example, CS 25.365),

(2) The amendment level of the existing type-certification basis for the certification specification, and

(3) The latest amendment level of the certification specification.

b. Step 2: Identify the Specific Hazard that the Requirement Certification Specification Addresses

(1) Each certification specification and subsequent amendments are intended to address a hazard or hazards. In this step the specific hazard(s) is/are identified. This identification will allow for a comparison of the effectiveness of amendment levels of the certification specification at addressing the hazard.

(2) In many cases the hazard and the cause of the hazard will be obvious. When the hazard and its related cause are not immediately obvious, it may be necessary to review the available background information from development and adoption of this certification specification (Explanatory Note and Comment/Response Document to the NPA. It may also be helpful to discuss the hazard with the Agency).

c. Step 3: Review the Consequences of the Hazard(s)

(1) Once the hazard has been identified, it is possible to identify the types of consequences that may occur because of the presence of the hazard. More than one consequence can be attributed for the same hazard. Typical examples of consequences would include, but are not be limited to:

• Incidents where only injuries occurred;

• Accidents where less than 10 % of the passengers died;

• Accidents where 10 % or more passengers died; and

• Accidents where a total hull loss occurred.

(2) The background information from development and adoption of the certification specification may provide useful information regarding the consequences of the hazard the requirement is intended to address.

d. Step 4: Identify the Historical and Predicted Frequency of Each Consequence

(1) Another source for determining impracticality is the historical record of the consequences of the hazard that led to a requirement or an amendment to a requirement. From these data, a frequency of hazard occurrence can be determined. It is important to recognise that the frequency of occurrence may be higher or lower in the future. Therefore, it is also necessary to predict the frequency of future occurrences.

(2) More than one consequence can be attributed for the same hazard. Therefore, when applicable, the combination of consequences and frequencies of those consequences should be considered together.

(3) The background information from development and adoption of the certification specification may provide useful information regarding the frequency of occurrence.

ED Decision 2011/010/R

01/12/2011

e. Step 5: Determine How Effective Full Compliance with the Latest Amendment of the Requirement Would Be at Addressing the Hazard

(1) When each amendment is promulgated, it is usually expected that compliance with the certification specification would be completely effective at addressing the associated hazard. It is expected that the hazard would be eliminated, avoided, or dealt with. However, in a limited number of situations, this may not be the case. It is also possible that earlier amendment levels may have addressed the hazard but were not completely effective. Therefore, in comparing the benefits of compliance with the existing typecertification basis to the latest amendment level, it is useful to estimate the effectiveness of both amendment levels in dealing with the hazard.

(2) It is recognised that the determination of levels of effectiveness is normally of a subjective nature. These are relative assessments of a qualitative nature that should not be treated as absolute determinations. Therefore, prudence should be exercised when making these determinations. In all cases, it is necessary to document the assumptions and data that support the determination.

(3) The following five levels of effectiveness are provided as a guideline:

(a) Fully effective in all cases. Compliance with the requirement eliminates the hazard or provides a means to avoid the hazard completely.

(b) Considerable potential for eliminating or avoiding the hazard. Compliance with the requirement eliminates the hazard or provides a means to avoid completely the hazard for all probable or likely cases, but it does not cover all situations or scenarios.

(c) Adequately deals with the hazard. Compliance with the requirement eliminates the hazard or provides a means to avoid the hazard completely in many cases. However, the hazard is not eliminated or avoided in all probable or likely cases. Usually this action only addresses a significant part of a larger or broader hazard.

(d) Hazard only partly addressed. In some cases compliance with the requirement partly eliminates the hazard or does not completely avoid the hazard. The hazard is not eliminated or avoided in all probable or likely cases. Usually this action only addresses part of a hazard.

(e) Hazard only partly addressed but action has negative side effect. Compliance with the requirement does not eliminate or avoid the hazard or may have negative safety side effects. The action is of questionable benefit.

f. Step 6: Determine Resource Costs and Cost Avoidance

(1) There is always cost associated with complying with a requirement. This cost may range from minimal administrative efforts to the resource expenditures that support full scale testing or the redesign of a large portion of an aircraft. However, there are also potential cost savings from compliance with a requirement. For example, compliance with a requirement may avoid aircraft damage or accidents and the associated costs to the manufacturer for investigating accidents. Compliance with the latest amendment of a certification specification may also facilitate certification of a product by the competent authority of a third country.

ED Decision 2011/010/R

01/12/2011

(2) When determining the impracticality of applying a certification specification at the latest amendment level, only the incremental costs and safety benefits from complying with the existing type-certification basis should be considered.

(3) When evaluating the incremental cost, it may be beneficial for the applicant to compare the increase in cost to comply with the latest certification specifications to the cost to incorporate the same design feature in a new aeroplane. In many cases an estimate for the cost of incorporation in a new aeroplane is provided in the regulatory evaluation by the Agency, which was presented when the corresponding certification specification was first promulgated. Incremental costs of retrofit/incorporation on existing designs may be higher than that for production. Examples of costs may include but are not limited to:

(a) Costs: The accuracies of fleet size projections, utilisation, etc. may be different than that experienced for derivative product designs and must be validated.

• Labour: Work carried out in the design, fabrication, inspection, operation or maintenance of a product for the purpose of incorporating or demonstrating compliance with a proposed action. Non-recurring labour requirements, including training, should be considered.

• Capital: Construction of new, modified or temporary facilities for design, production, tooling, training, or maintenance.

• Material: Cost associated with product materials, product components, inventory, kits, and spares.

• Operating Costs: Costs associated with fuel, oil, fees, and expendables.

• Revenue/Utility Loss: Costs resulting from earning/usage capability reductions from departure delays, product downtime, capability reductions of performance loss due to seats, cargo, range, or airport restrictions.

(b) Cost Avoidance:

• Avoiding cost of accidents, including investigation of accidents, lawsuits, public relations activities, insurance, and lost revenue.

• Foreign Certification: Achieve a singular effort that would demonstrate compliance to the requirements of most certifying agencies, thus minimising certification costs.

g. Step 7: Document Conclusion. Once the information from previous steps has been

documented and reviewed, the applicant’s position and rationale regarding practicality can be documented. Examples of possible positions would include, but are not limited to:

(1) Compliance with the latest certification specification is necessary. The applicant would pursue the change at the latest amendment level.

(2) Compliance with an amendment level between the existing type-certification basis and the latest amendment would adequately address the hazard at an acceptable cost, while meeting the latest amendment level would be impractical. The applicant would then propose the intermediate amendment level of the certification specification.

(3) The increased level of safety is not commensurate with the increased costs associated with meeting the latest amendment instead of the existing type-certification basis. Therefore, the applicant would propose the existing type-certification basis.

ED Decision 2011/010/R 01/12/2011

(4) The results of this analysis were inconclusive. Further discussions with the Agency are warranted.

Note: This process may result in a required type-certification basis that renders the proposed

modification economically not viable.

3. Examples of How to Certify Changed Aircraft. The following examples are for large

aeroplanes and illustrate the typical process an applicant follows. The process will be the same for all product types.

a. Example 1: CS 25.963 (e) Fuel Tank Access Covers

(1) This change is part of a significant large aeroplane change that increases passenger payload and gross weight by extending the fuselage by 20 feet. To accommodate the higher design weights and increased braking certification specification, and to reduce runway loading, the applicant will change the landing gear from a two-wheel to four-wheel configuration; this changes the debris scatter on the wing from the landing gear. The new model aeroplane will be required to comply with the latest applicable regulations based on the date of application.

(2) The wing will be strengthened locally at the side of the body and at the attachment of engines and landing gear, but the applicant would not like to alter wing access panels and the fuel tank access covers. Although the applicant recognises that the scatter pattern and impact loading on the wing from debris being thrown from the landing gear will change, he proposes that it would be impractical to redesign the fuel tank access covers.

(3) Step 1: Identify the Regulatory Change Being Evaluated

(a) The existing certification basis of the aeroplane that is being changed is CS-25 prior to Amendment3.

(b) Amendment 3 to CS-25 added the requirement that fuel tank access covers on large aeroplanes be designed to minimise penetration by likely foreign objects, and be fire resistant.

(4) Step 2: Identify the Specific Hazard that the Regulation Addresses

Fuel tank access covers have failed in service due to impact with high-energy objects such as failed tire tread material and engine debris following engine failures. In one accident, debris from the runway impacted a fuel tank access cover, causing its failure and subsequent fire, which resulted in fatalities and loss of the aeroplane. Amendment 3 ensures that all access covers on all fuel tanks are designed or located to minimise penetration by likely foreign objects, and are fire resistant.

(5) Step 3: Review the History of the Consequences of the Hazard(s)

Occurrences with injuries and with more than 10 % deaths.

(6) Step 4: Identify the Historical and Predicted Frequency of Each Consequence

(a) In 200 million departures of large jets: • One occurrence with more than 10 % deaths; and

• One occurrence with injuries.

(b) There is no reason to believe that the future rate of accidents will be significantly different than the historical record.

ED Decision 2011/010/R 01/12/2011

(7) Step 5: Determine How Effective Full Compliance with the Latest Amendment of the Regulation Would Be at Addressing the Hazard

(a) Considerable potential for eliminating or avoiding the hazard.

(b) Compliance with Amendment 3 eliminates the hazard or provides a means to avoid the hazard completely for all probable or likely cases. However, it does not cover all situations or scenarios.

(8) Step 6: Determine Resource Costs and Cost Avoidance

(a) Costs: • For a newly developed aeroplane, there would be minor increases in labour resulting from design and fabrication.

• There would be a negligible increase in costs related to materials, operating costs, and revenue utility loss.

(b) Cost Avoidance: • There were two accidents in 200 million departures. The applicant believes that it will manufacture more than 2 000 of these aeroplanes or derivatives of these aeroplanes. These aeroplanes would average five flights a day. Therefore, statistically there will be accidents in the future if the hazard is not alleviated. Compliance will provide cost benefits related to avoiding lawsuits, accident investigations, and public relation costs.

• There are cost savings associated with meeting a single type-certification basis for the Agency and foreign regulations.

(9) Conclusion. It is concluded that compliance with the latest certification specification

increases the level of safety at a minimal cost to the applicant. Based on the arguments and information presented by the applicant through the Certification Review Item (CRI) process, the Agency determined that meeting the latest amendment would be practical.

b. Example 2: 14 CFR § 25.365 Pressurised Compartment Loads

NOTE: This example is taken from the FAA certification experience gained before the Agency’s start, so references to FAR sections and amendments are kept.

(1) This example is a passenger to freighter conversion STC.

(2) This change affects the floor loads on the airplane as well as the decompression venting.

(3) Step 1: Identify the Regulatory Change Being Evaluated

(a) The existing certification basis of the airplane that is being changed includes 14 CFR § 25.365 at Amendment 25-40. The initial release of 14 CFR § 25.365 required that the interior structure of passenger compartments be designed to withstand the effects of a sudden release of pressure through an opening resulting from the failure or penetration of an external door, window, or windshield panel, or from structural fatigue or penetration of the fuselage, unless shown to be extremely remote.

(b) Amendment 25-54 revised 14 CFR § 25.365 to require that the interior structure be designed for an opening resulting from penetration by a portion of an engine, an opening in any compartment of a size defined by 14 CFR § 25.365(e)(2), or the maximum opening caused by a failure not shown to be extremely improbable. The most significant

ED Decision 2011/010/R 01/12/2011

change is the “formula hole size” requirement introduced into § 25.365(e)(2) at Amendment 25-54.

(c) Amendment 25-71/72 (Amendments 25-71 and 25-72 are identical) extended the requirement to all pressurised compartments, not just passenger compartments, and to the pressurisation of unpressurised areas. Pressurisation of unpressurised areas had previously been identified as an unsafe feature under 14 CFR § 21.21(b)(2).

(d) Amendment 25-87 redefined the pressure differential load factor that applies above an altitude of 45 000 feet. Compliance with Amendment 25-87 is not affected since the airplane does not operate above an altitude of 45 000 feet. The applicant proposes to meet the “pressurisation into unpressurised areas” requirement introduced in Amendment 25-71/72. The applicant does not propose to comply with the formula hole size requirement introduced in § 25.365(e)(2) at Amendment 25-54.

(4) Step 2: Identify the Specific Hazard that the Regulation Addresses

The hazard is a catastrophic structure and/or system failure produced by a sudden release of pressure through an opening in any compartment in flight. This opening could be caused by an uncontained engine failure, an opening of a prescribed size due to the inadvertent opening of an external door in flight, or an opening caused by a failure not shown to be extremely improbable. The opening could be produced by an event that has yet to be identified.

(5) Step 3: Review the History of the Consequences of the Hazard(s)

Occurrences with injuries, less than 10 % deaths, and more than 10 % deaths.

(6) Step 4: Identify the Historical and Predicted Frequency of Each Consequence

(a) In 200 million departures of large jets:

• Two occurrences with more than 10 % deaths; • One occurrence with less than 10 % deaths; and • One occurrence with injuries.

(b) There is no reason to believe that the future rate of accidents will be significantly different than the historical record.

(7) Step 5: Determine How Effective Full Compliance with the Latest Amendment of the Regulation Would Be at Addressing the Hazard

(a) Compliance with the latest amendment eliminates the hazard or provides a means to avoid the hazard completely.

(b) Design changes made to the proposed derivative airplane bring it closer to full compliance with 14 CFR § 25.365 at Amendment 25-54. The original airplane was shown to meet the requirements for a hole size of 1.1 square feet. Amendment 25-54 would require a hole size of 5.74 square feet, and the current reinforcements for the converted airplane can sustain a hole size of 3.65 square feet in the forward area and 2.65 at the aft area. This is 3.1 and 2.4 times respectively better than the original design condition of Amendment 25-0 and is a significant improvement over the worldwide passenger fleet in service.

(8) Step 6: Determine Resource Costs and Cost Avoidance

(a) Costs: There would be savings in both labour and capital costs if compliance were shown to Amendment 25-0 instead of Amendment 25-54. Major modifications to the floor

ED Decision 2011/010/R 01/12/2011

beams would be necessary to meet the formula hole size requirement in Amendment 25- 54.

(b) Cost Avoidance:

(1) There were four accidents in 200 million departures. The applicant believes that it will manufacture more than 2 000 of these airplanes or derivatives of these airplanes. These airplanes would average two flights a day. Therefore, statistically there will be accidents in the future if the hazard is not alleviated. Compliance will provide cost benefits related to avoiding lawsuits, accident investigations, and public relation costs.

(2) There are cost savings associated with meeting a single certification basis for FAA and foreign regulations.

(9) Step 7: Document Conclusion Regarding Practicality. The design complies with

14 CFR § 25.365 at Amendment 25-0, 25-71/72, and 25-87, and is nearly in full compliance with Amendment 25-54 (and certain aspects of Amendments 25-71/72 and 25-87). The design would adequately address the hazard at an acceptable cost. Therefore, based on arguments of impracticality discussed in an issue paper, the FAA accepts the applicant’s proposal to comply with 14 CFR § 25.365 at Amendment 25-0.

ED Decision 2011/010/R 01/12/2011 The Appendix 3 to GM 21A101 is amended as follows:

Appendix 3C to GM 21A.101. THE USE OF SERVICE EXPERIENCE IN THE CERTIFICATION PROCESS

1. Introduction.

Service experience may support the application of an earlier airworthiness standard if, in conjunction with the applicable service experience and other compliance measures, the earlier standard provides a level of safety comparable to that provided by the latest certification specifications. The applicant must provide sufficient substantiation to allow the Agency to make this determination. A statistical approach may be used, subject to the availability and relevance of data, but sound engineering judgment should be used as a minimum. For service history to be acceptable, the data must be both sufficient and pertinent. The essentials of the process involve:

a. A clear understanding of the requirement change and the purpose for the change and

hazard addressed;

b. A determination based on detailed knowledge of the proposed design feature;

c. The availability of pertinent and sufficient service experience data; and

d. A comprehensive review of that service experience data.

2. Guidelines.

The Certification Review Item (CRI) process (either a stand-alone CRI or included in the CRI.A- 1) would be used, and the applicant should provide documentation to support the following:

a. The identification of the differences between the certification specification in the existing

basis and the certification specification as amended, and the effect of the change in the certification specification.

b. A description as to what aspect(s) of the latest certification specifications the proposed

changed product would not meet.

c. Evidence showing that the proposed type-certification basis for the changed product,

together with applicable service experience, relative to the hazard, provides a level of safety consistent with complying with the latest certification specifications.

d. A description of the design feature and its intended function.

e. Data for the product pertinent to the certification specification.

(1) Service experience from such data sources as the following: (a) Accident reports; (b) Incident reports; (c) Service bulletins; (d) Airworthiness directives; (e) Repairs;

ED Decision 2011/010/R 01/12/2011 (f) Modifications; (g) Flight hours/cycles for fleet leader and total fleet; (h) World airline accident summary data; (i) Service difficulty reports; (j) Reports from Accident Investigation Boards (k) Warranty, repair and parts usage data. (2) Show that the data presented represent all relevant service experience for the product, including the results of any operator surveys, and is comprehensive enough to be representative. (3) Show that the service experience is relevant to the hazard. (4) Identification and evaluation of each of the main areas of concern with regard to: (a) Recurring and/or common failure modes; (b) Cause; (c) Probability, by qualitative reasoning; and (d) Measures already taken and their effects. (5) Relevant data pertaining to aircraft of similar design and construction may be included. (6) Evaluation of failure modes and consequences through analytical processes. The analytical processes should be supported by: (a) A review of previous test results; (b) Additional detailed testing as required; (c) Review aircraft Functional Hazard Assessments (FHA) and any applicable System Safety Assessments (SSA) as required.

f. A conclusion that draws together the data and the rationale.

g. These guidelines are not intended to be limiting, either in setting required minimum

elements or in precluding alternative forms of submission. Each case may be different, based on the particulars of the system being examined and the certification specification to be addressed.

3. Example:

NOTE: This example is taken from a FAA certification gained prior to the Agency’s start, so references to FAR sections and amendments are kept.

a. The following example, for transport airplanes (14 CFR § 25.1141(f) Auxiliary Power Unit

(APU) Fuel Valve Position Indication System), illustrates the typical process an applicant follows. The process will be the same for all product types.

ED Decision 2011/010/R

01/12/2011

b. This example comes from a derivative model transport airplane where significant changes

were made to the main airframe components, engines and systems, and APU. The baseline airplane has an extensive service history. The example shows how the use of service experience supports a finding that compliance with the latest regulation would not contribute materially to the level of safety and that application of the existing certification basis (or earlier amendment) would be appropriate. The example is for significant derivatives of large aeroplanes with extensive service history, and illustrates the process, following the guidelines in this appendix, but does not include the level of detail normally required.

(1) Determine tThe differences between the regulation in the existing certification basis and the regulation as amended, and the effect of the change in the requirement.

The existing certification basis of the airplane that is being changed is the initial release of Part-25. Amendment 25-40 added requirement 14 CFR § 25.1141(f), which mandates that power-assisted valves must have a means to indicate to the flight crew when the valve is in the fully open or closed position, or is moving between these positions. The addressed hazard would be risk of APU fire due to fuel accumulation caused by excessive unsuccessful APU start attempts.

(2) What aspect of the proposed changed product would not meet the latest regulations?

The proposed APU fuel valve position indication system does not provide the flight crew with fuel valve position or transition indication and, therefore, does not comply with the requirements of 14 CFR § 25.1141(f).

(3) Evidence that the proposed type-certification basis for the changed product, together with applicable service experience and other compliance measures provide an acceptable level of safety

The APU fuel shut-off valve and actuator are unchanged from those used on the current family of airplanes, and have been found to comply with the earlier Amendment 25-11 of 14 CFR § 25.1141(f). The existing fleet has achieved approximately (#) flights during which service experience of the existing design has been found to be acceptable. If one assumes a complete APU cycle, i.e., start-up and shutdown for each flight, the number of APU fuel shut-off valve operations would be over 10 cycles, which demonstrates that the valve successfully meets its intended function and complies with the intent of the regulation. In addition, the system design for the changed product incorporates features that increase the level of functionality and safety.

(4) A description of the design feature and its intended function

The fuel shut-off valve, actuator design, and operation is essentially unchanged; with the system design ensuring that the valve is monitored for proper cycling from closed to open at start. If the valve is not in the appropriate position (i.e. closed), then the APU start is terminated, an indication is displayed on the flight deck, and any further APU starts are prevented. Design improvements using the capability of the APU Electronic Control Unit (ECU) have been incorporated in this proposed product change. These design changes ensure that the fuel valve indication system will indicate failure of proper valve operation to the flight crew, but the system does not indicate valve position as required by 14 CFR § 25.1141(f).

(5) Data for the product pertinent to the requirement

The FAA and applicant record the data in an issue paper (G-1 or a technical issue paper). An issue paper was coordinated, included data, or referenced reports, documenting relevant service experience that has been compiled from incident reports, fleet flight hour/cycle data, and maintenance records. The issue paper also discussed existing and proposed design details, failure modes and analyses showing to what extent the proposed airplane complies with the

ED Decision 2011/010/R 01/12/2011

latest amendment of 14 CFR § 25.1141. Information is presented to support the applicant’s argument that compliance with the latest amendment would not materially increase the level of safety. Comparative data pertaining to aircraft of similar design and construction are also presented.

(6) The conclusion, drawing together the data and rationale

Conclusion is documented in the G-1 issue paper. The additional features incorporated in the APU fuel shut-off valve will provide a significant increase in safety to an existing design with satisfactory service experience. The applicant proposes that compliance with the latest amendment would not materially increase the level of safety and that compliance with 14 CFR § 25.1141 at Amendment 25-11 would provide an acceptable level of safety for the proposed product change.

ED Decision 2011/010/R 01/12/2011 A new appendix D to GM 21A101 is introduced as follows:

Appendix D to GM 21A.101.

TABLES AND FIGURES TO ASSIST CPR UNDERSTANDING

Figure 3: Affected and Not affected area

Affected Area Unaffected

Area

Secondary Changes Changed Area

ED Decision 2011/010/R 01/12/2011

Figure 4: Example of Related and Unrelated changes –Increase in Maximum Number of Passengers

Figure 4: Example of Related and Unrelated changes

Grouping of related changes (Significant change)

Unaffected Area

ED Decision 2011/010/R 01/12/2011

Figure 5: Establishing TC basis for Substantial, Significant and Not significant changes according to 21A.101 (a) and ((b)

ED Decision 2011/010/R 01/12/2011

Figure 6: Establishing TC basis for a Change on Excepted Products (21A.101(c))

ED Decision 2011/010/R 01/12/2011

A new appendix E to GM 21A101 is introduced as follows:

Appendix E to GM 21A.101. Related Part-21 Requirements

• 21A.16A, Airworthiness codes • 21A.16B, Special conditions • 21A.17, Type-certification basis • 21A.18, Designation of applicable environmental protection requirements and certification specifications • 21A.19, Changes requiring a new type-certificate • 21A.21, Issue of type-certificate • 21A.23, Issue of a restricted type-certificate • 21A.90, Scope • 21A.91, Classification of changes in type design • 21A.93, Application • 21A.95, Minor changes • 21A.97, Major changes • 21A.101, Designation of applicable certification specifications and environmental protection requirements • 21A.103, Issue of approval • 21A.111, Scope • 21A.113, Application for a supplemental type-certificate • 21A.114, Showing of compliance • 21A.115, Issue of a supplemental type-certificate • 21A.117, Changes to that part of a product covered by a supplemental type-certificate • 21A.604(b), 21A.604 ETSO Authorisation for an auxiliary power unit (APU)